Several of Ashoka's inscriptions appear to have been set up near towns, on important routes, and at places of religious significance. Many of the inscriptions have been discovered in hills, rock shelters, and places of local significance. Various theories have been put forward about why Ashoka or his officials chose such places, including that they were centres of megalithic cultures, were regarded as sacred spots in Ashoka's time, or that their physical grandeur may be symbolic of spiritual dominance. Ashoka's inscriptions have not been found at major cities of the Maurya empire, such as Pataliputra, Vidisha, Ujjayini, and Taxila.