This stirring site dates to the 15th century, when a monument-filled town named Khalifatabad was built under the watch of Khan Jahan Ali and the governing Bengal Sultanate. The town included a slew of arresting mosques, several elaborate bridges and, eventually, the tomb of ruler Khan Jahan Ali himself. The mosques here are still used for daily worship, but climate change and the resultant rising sea levels have led to severe flooding in the area, putting these precious landmarks at severe risk.