The Khajuraho temples are made of sandstone, with a granite foundation that is almost concealed from view. The builders didn't use mortar: the stones were put together with mortise and tenon joints and they were held in place by gravity. This form of construction requires very precise joints. The columns and architraves were built with megaliths that weighed up to 20 tons. Some repair work in the 19th Century was done with brick and mortar; however, these have aged faster than original materials and darkened with time, thereby seeming out of place.