Vellore Fort, built in the 17th century by a chieftain of the Vijayanagar empire
, is one of the superb specimens of military architecture in South India. The strongest fortress in South India, it has double walls. The main walls are made of huge granite blocks laid one over the other without using mortar. The fort witnessed the killing of European soldiers in a revolution at 1806, instigated by the second son of Tipu Sultan
. Inside the fort complex there is a small museum that displays the sculptures of Chola and Pallava periods. The fort houses the Jalagandeeswarar temple built around 1550, and many buildings now used as public offices.