The Bengal Sultanate (1352–1576) normally used brick as the primary construction material of large buildings, as pre-Islamic buildings had done. Stone had to be imported to most of Bengal, whereas clay for bricks is plentiful. But stone was used for columns and prominent details, usually re-used from Hindu or Buddhist temples. The early 15th century Eklakhi Mausoleum at Pandua, Malda or Adina, is often taken to be the earliest surviving square single-domed Islamic building in Bengal, the standard form of smaller mosques and mausoleums. But there is a small mosque at Molla Simla, Hooghly district, that is possibly from 1375, earlier than the mausoleum. The Eklakhi Mausoleum is large and has several features that were to become common in the Bengal style, including a slightly curved cornice, large round decorative buttresses at the corners, and decoration in carved terracotta brick.