The Ratna style is a characteristic style of Bengali temple architecture, that flourished in eastern India during the 17th - 18th centuries. A ratna (jewel) type of temple has a curved cornice with one or more towers or pinnacles on its roof. The simplest form will have a single central tower ('ek-ratna' or 'single jewel'). With the addition of small towers at the four corners, the style becomes 'panch ratna' or 'five jewels.' What is remarkable is the striking resemblance to Mughal architecture evidenced in the triple arched porch, terracotta front, and small dome,characteristic of the mosques and shrines. The ratna style combined features of the Sultanate mosques and thatched houses. Some of the temples built in this style had second-storey rooms, which were considered the pleasure grounds of the gods. The ratna style temples can be differentiated from the mosques by their porches and corridors on all the four sides, and by the staircase that led to the second storey.
With increase in the number of storeys, the ratnas also could go up to nine, thirteen, seventeen, twenty-one or twenty five. The earliest temples of the 17th century were built by the Malla kings of Bishnupur.
Striking examples of panch-ratna temples are The Vrindavana Chandra Temple in Gobarhati, Murshidabad, built in the year 1772, the Radha-Govinda temple of Chechua-Gobindanagar, Midnapore dating back to 1781, and the Sridhara Temple of Asanda, Howrah, belonging to 1789. Interestingly, the panch-ratna and nava-ratna (nine jewels) styles seem to have developed earlier than the ek-ratna.
The nava-ratna is actually a pancha-ratna temple, with an extra storey and four corner turrets. The Shyama-Sundara Temple in Sonabaria, Khulna, dated 1767 and the Radha-Damodara Temple of 1796 in Indas, Bankura are fine examples of nava-ratna temples.