Khania Dighi Mosque also called Rajbibi Masjid, is located on the western bank of Khania Dighi, which is about a quarter mile away from the high mud wall of the ancient city of Gaur on the north and the Balia Dighi on the west in Nawabganj district. The building is now in a good state after thorough repairs undertaken by the Directorate of Archaeology, Bangladesh. Built mainly of bricks, the mosque consists of a square prayer chamber, 29 ft a side, and a verandah of 29 ft by 9 ft 6 ins in the east. The prayer chamber is roofed over by a large hemispherical dome, while the verandah is covered by three small domes. The large dome of the prayer chamber is carried on half-domed squinches on the corners and blocked arches on the four cardinal sides and the pendentives in between the arches. The three small domes of the verandah are built on pendentives. The prayer hall is entered by three archways from the verandah which correspond in height and width to the three archways on the eastern facade and a single archway from the north and south sides. The four exterior angles of the building are marked by octagonal towers rising upto the roof level. Two other towers distinguish the points where the verandah joins the prayer chamber. All the towers are divided into sections by raised bands. The cornice of the building is slightly curved.