By the 16th century Conisbrough Castle was in a poor state of repair, and a royal survey carried out in 1537 and 1538 showed that the gates, bridge and parts of the walls had collapsed in a spectacular land slippage, and that one floor of the keep had also fallen in. The collapse of the walls was a consequence of the instability of the topsoil on top of the limestone spur, which was a mixture of clay and sandstone; once the clay was washed away over time, the remaining sandstone proved extremely unstable and liable to crack.