Vaishnavism swept through Bengal in the 16th century and inspired three centuries of temple-building, during which thousands of temples were sponsored by kings, merchants, and zamindars. The patrons and sutradhars (architects) of these temples clearly valued experimentation and individuality. In fact there are so many variations in architectural styles that the temples defy easy architectural classification.

Despite this diversity, Bengal's brick temples have in common some distinctive features, derived from a range of influences. Sloping roofs and curved eaves are derived from Bengali huts, the arched entrances and internal domes are Persian, the surface terracotta ornamentation from the 8th century Pala Buddhist architecture, and the ridged turrets from Orissan temples. In the late-19th century, we also start seeing European influences in the architecture: such as neo-classical porch columns and parapets with statuary.

In the 1970s, a group of researchers including David McCutchion, Tarapada Santra, Hitesranjan Sanyal, and Amiyakumar Bandyopadhyay, extensively studied and documented Bengal’s temples. They pioneered a classification system based on the temples’ superstructures, that we still use today. This classification has roots in sutradhara vocabulary but was refined and systematized, mainly by David McCutchion.

The earliest temples in Bengal are deuls. This is an ancient architectural style that was common in India from the 6th century onward. The particular type of deul that is common in Bengal is called rekha deul (an Orissan name), and is characterized by a square sanctum, vertical projections (rekha) on the walls, a curvilinear tower, and chaitya (mesh) decoration on the facades. The temples have a large amalaka (ridged disc) and kalasa (pot) finial at the top. Only a few early Bengali deuls remain, but among them some brick-built examples are monumental and impressive. When the rekha style reappeared in the 16th century, it was completely transformed by features such as internal domes, arches, and terracotta decorated facades. Many such temples were built in the 19th century although they were mostly much smaller than the pre-Islamic deuls. The turrets of ratna temples, especially the central towers of pancha-ratna and nava-ratna temples, are also usually built as rekha deuls.

The earliest example of the early rekha deul style is the 9th century stone Siddheswara temple at Barakar in Bardhaman. Examples of the 11th century massive brick-built deuls are at Satdeulia (Bardhaman), Bahulara (Bankura), and Jatar Deul (24 Parganas). The examples after the 16th century can be grouped into deuls with smooth towers, such as at Rajnagar in Medinpur, and those with ridged towers which were built in large numbers in the 19th century in Bardhaman and Birbhum. Decorated and well-preserved examples of ridged rekha deuls are the Pratapesvara temple at Kalna, temples at Ilambazar in Birbhum, and at Mankar and Debipur in Bardhaman.

The ek-bangla (or do-chala) structure consists of two sloping roofs with curved edges or cornices meeting at a curved ridge. Internally, there is a single rectangular chamber covered by a vaulted roof. This style imitates single-celled domestic huts in Bengal and was first adopted in Islamic architecture, the earliest example being the 17th century mausoleum of Fateh Khan at Gaur. Although simple in structure, temples of this style are rare. A variant is the jor-bangla temple, with two adjacent, connected do-chala temples, one as a porch, and the other as the shrine, with a central upper turret.

The best-preserved group of Bangla temples is at Baronagar near Murshidabad, where Rani Bhabani built many temples in this style, including the char-bangla complex: a group of four ek bangla temples facing each other across a courtyard. One of the earliest and most impressive examples of the Bangla style is Jor-Bangla Keshtaraya temple, built in Bishnupur in the 17th century. Baronagar also has a fine example of this style, the Gangesvara temple, which has very rich terracotta decoration.

In this type of temple, four triangular roofs meet at a point, with the edges of each chala and also of the cornices curved. For some reason, the char-chala style is very rare except in the districts of Birbhum, Murshidabad, and Nadia. In Nadia it seems to have been the preferred style of the Nadia rajas. Most char-chala temples are relatively small and have a single entrance.

A well-preserved and early example of the char-chala temple is the Raghavesvara temple at Diknagar in Nadia. Other examples in Nadia are the Jalesvara temple at Santipur and the temples at Palpara and Sibnibas. The patrons of the temples at Maluti (now in Jharkhand) and at Ganpur in Birbhum, also favoured this style. Other notable examples of the char-chala style are: the early 17th century Raghunatha temple at Ghurisa in Birbhum, and the Govinda temple in Puthia in Bangladesh, which is a rare example of a char-chala temple with a triple-arched entrance.

If the roof of a char-chala temple is truncated and a miniature char-chala temple is added on it, then it becomes an at-chala temple. Though the char-chala style is rare, the at-chala style is very common, particularly in Hugli and Howrah, where it became very popular with artisans and patrons in the 18th and 19th centuries. As the architecture of the at-chala temple became common, the decorative arrangements of terracotta panels on the facade also became standardised, resulting in hundreds of similar at-chala temples in this region, many with richly sculpted facades.

Many variations of the basic at-chala style were developed. These range from a small squat Bishnupuri type where the roofs are only slightly separated, to a massive type where the temple is placed on a high plinth. The most common type has triple-arched entrance and fully-decorated facades. This style is widespread across Hugli, Howrah, Medinipur, and Bankura districts. Some famous examples of at-chala temples are at Gurap, Mellock, the temples at Atpur, the Dakshina Kali temple at Malancha in Medinipur, temples at Amadpur in Bardhaman, and temples in villages around Arambagh in Hugli. The renowned but significantly renovated pilgrimage temples at Kalighat and Tarakeswar are also in the atchala style.

Ek Ratna temples were a particular favourite of the Malla rulers who built many such temples at their capital in Bishnupur. Most of these temples are unadorned and built of laterite rather than brick. An exception is the lavishly decorated Madan Mohan temple, which has a facade fully decorated with large terracotta panels. In a slightly different style (with octagonal chala turrets) are the ek-ratna temples at Guptipara and Bansberia, both remarkable for the extent, quality and content of their terracotta decoration. Elsewhere, ek-ratna temples are rare but where they do exist they are usually from the 17th or early 18th century, such as at Daspur in Medinipur and the recently discovered, magnificent Damodar temple at Kendur in Bardhaman.

In the five-towered (pancha-ratna) style, the superstructure consists of a large central tower and four smaller towers at the corners. This layout (particularly the construction of the turrets as small temples) recalls the auspicious panchayatana temple style of northern India (as at Khajuraho and Deogarh) where the main temple is surrounded by smaller temples at four corners of the plinth. The Malla kings built some impressive early examples of pancha-ratna temples such as the Shyamaraya temple at Bishnupur and the monumental Gokulchand temple at Gokulnagar.

Alhough some of the finest pancha-ratna temples are from 17th century Bishnupur, the style was adopted by landlords and merchants in the 19th century, particularly in Medinipur and Bankura district, where there are many examples such as the Gopinath temple at Radhakantapur, the Radha-Govinda temple at Chechua-Gobindanagar, and the Radhakanta temple at Akui. There are some notable examples outside these districts as well, such as the Govinda temple at Puthia and the Gopinath temple at Dasghara.

The next level of elaboration after the pancha-ratna is the nine-towered, naba-ratna temple which is a pancha-ratna with an extra story. Though elaborate, this style was popular in and around Bishnupur, and in the nearby districts of Hugli and Medinipur. The large number of pinnacles give smaller temples in this style an exaggerated grandeur that was clearly a source of prestige to patrons. Temples with even more complex superstructures were built by increasing the number of levels and adding more turrets at each level. The most elaborate pinnacled style is the twenty-five-spired (pancha-vimsati-ratna) temple which was patronized by the powerful zamindars of Bardhaman who built three such massive and elaborate temples at the royal centre at Kalna. In most ratna temples, the upper stories are not merely decorative but also used in daily rituals. Deities are taken up to the pavilions in the first or the second tower to rest or to take the cool evening breeze, and so that the worshippers gathered on the temple grounds can view them.

The greatest naba-ratna temple is the massive and richly decorated early 18th century Kantaji temple at Kantanagar in Dinajpur (Bangladesh). Nearly all other naba-ratna temples are from the 19th century or later, including the renowned modern temples of Dakshineswar and Talpukur near Kolkata. Other notable examples of naba-ratna temples are the Radha Binod temple in Kenduli, the temples at Joypur, the Sridhara temple in Bishnupur, the Santinatha Siva temple in Chandrakona, and the temples at Dubrajpur in Birbhum.

Although octagonal terracotta temples are rare, they deserve separate discussion. Richly decorated octagonal temples with terracotta panels on all eight sides and rekha deul superstructures were built in the 19th century in the Bardhaman-Birbhum area. Less decorated examples with chala superstructures also exist. Another octagonal style specific to a single patron (Rani Bhabani) consists of large open temples with inverted lotus-dome.

The best examples of richly decorated octagonal rekha deuls are at Sribati, Ilambazar, Banpas, and Supur. The Chandranatha Siva temple in Hetampur is a rare example of an octagonal temple with a nava-ratna superstructure. This temple is also unusual for the style and subject-matter of sculpture on its walls: it has sculpture of Queen Victoria, and Prince Albert, surrounding images of Durga Mahisamardhini and Siva with Parvati. The best example of the special octagonal temple style patronized by Rani Bhabani is the Bhavanisvara temple at Baranagar in Murshidabad but examples also exist elsewhere in her domains such as at Pabna.

The flat-roofed temple style became common from the 19th century onwards, particularly in Medinipur district. Such temples usually lack a superstructure, but otherwise adopt the standard features of late-medieval temples of Bengal, such as cusped triple-arched entrances, octagonal or clustered pillars, terracotta decorated facades, and often, internal domes or vaults. The Medinipur sutradharas differentiated between large flat-roofed temples which they called dalan (the most common example of this being the Durgadalan for the annual Durga Puja common in many 19th century zamindar palaces), and smaller flat-roofed temples, which they called chandni. Towards the late 19th century, European influences became common in these temples.

The Rupesvara temple within the Kalna temple complex and the Raghunatha temple of the Nayak family at Bahadurpur in Bardhaman are examples of the decorated flat-roofed temple style. Dalan temples with modern pillars and stucco decoration are common in Medinpur, especially at Chandrakona and Ghatal, but several examples also exist at Mankar near Bardhaman town.

Temples of identical style and size are often grouped together, arranged in a geometrical pattern. The most common layout is twelve at-chala Siva temples (called baro or dvadasa siva temple) arranged in two separate sets of six temples and placed along a straight line, often along a river bank). Two identical temples (also usually at-chala and dedicated to Siva placed side by side, is called jora siva temple and is very common. Some temple complexes have four temples facing inward onto a courtyard. The most elaborate grouping that exists is of a hundred-and-eight Siva temples arranged geometrically.

Twelve at-chala Siva temples along a riverbank are fairly common. Famous examples are at Dakshinesvar and Talpukur (attached to the main nava-ratna temple), but twelve siva temples also exist independently, as at Konnagar. At Sukharia, twelve temples (2 pancha-ratna, 10 at-chala) are attached to a twenty-five ratna temple. Groups of four temples facing inward onto a courtyard can be seen at Baronagar and at Guptipara. There are only two instances of one-hundred-and-eight temples, and both in Bardhaman district and built by the Bardhaman rajas. At Kalna they are placed in two concentric circles, and at Nababhat in Bardhaman town, they are in a large rectangle.

Most Hindu temples have a porch next to the sanctum, where worshippers may gather to view the deity (darsana) and receive blessed food (prasada). In Bengali terracotta temple architecture, the porch and the sanctum are usually within the same building. But there are many instances where separate (often richly decorated) porches are added to the front of the temple. These porches are themselves in bangla, chala, or dalan styles. Some porch combinations are more common than others. Medinipur, for instance, has many examples of a rekha-deul with a char-chala porch. Besides attached porches, temple complexes sometimes contain separate subsidiary mandapas such as bhoga-mandapa (for preparing or distributing prasada), nata-mandapa (for festivals), and nahabat-khana (ceremonial entrance hall).

Temples with richly decorated porches are the Krishna temple at Baidyapur (rekha porch on a rekha deul), the Lakshmi Janardan temple at Debipur (bangla porch on a rekha deul), Siva temple at Kasimbazar-Byaspur (bangla porch on a domed temple), the Radha-Govinda temple at Atpur (char-chala porch on an at-chala temple), and the Krishnachandra temple at Kalna. Examples of separate, subsidiary porches within temple complexes are the bhoga-mandapa of the Madana Mohana temple at Bishnupur, ek-bangla gateway of the Radha Madhab temple at Bishnupur, and the flat-roofed nahabat-khana at the Brindabanchandra complex at Guptipara.

The term mancha means a raised pavilion. Many types of such pavilions were built in the temple compounds, mainly to house idols during important Krishna festivals, when month-long fairs and kirtans where held around these structures. The rasmancha is the focus of the autumn ras festival and is usually octagonal with arched openings on each side and roofs with eight turrets surrounding a large central tower. In Medinipur, a special type of turret was developed for rasmanchas, with a bulging vase-like base capped by an inverted flower. The Daspur sutradharas called this rasun-chura (garlic-pinnacled). Manchas are usually smaller than the main temple, but in some sites, large pyramidal manchas were built, to which idols from various temples in the vicinity were brought on festival days (such as at Puthia and Bishnupur).

Ornate rasmanchas are particularly common in Medinipur with examples at Saulan, Ajuria, and Alangiri. Notable examples outside Medinipur is the rasmancha of Bara-taraf at Hadal-Narayanpur and at Rajogram in Bankura. Examples of monumental rasmanchas are at Narajol and Bishnupur, where a large pyramidal structure was built by the Mallas for their annual ras festival.

The dolmancha was the focus of the springtime doljatra festival during which the temple deity was ceremonially carried out of the main temple and temporarily installed in this structure. It is usually on a high plinth, has four columns or wall sections, and char-chala, pancharatna, or rekha roofs.

Notable examples of terracotta decorated dolmanchas are at Rautara in Howrah, and at Gurap and Talchinan both in Hugli district. There are very large many-storied and pyramidal dolmanchas at Rajshahi and at Pabna in Bangladesh.