The 83m high Rock Fort is the only outcrop in the otherwise flat land of the city. The rock is one of the oldest in the world-approximately 3.800 million years, which makes it as old as the rocks of Greenland and older than the Himalayas. The sheer abruptness of its rise is a thrill in itself, but the actual centre of attraction is not the fort itself, of which very little remains, but the temple at the summit. 344 steps hewn out of rock lead to the top where there are inscriptions dating back to the 3rd century.B.C. Hardly anything remains of the ramparts but the Main Guard Gate is still intact. The fort played an important part during the Carnatic wars and according to an inscription, mainly contributed to lay the foundations of the British Empire in India.
At the top of the rock is the Uchipillaiyar Koil, a temple dedicated to Lord Vinayaka from where one can enjoy a panoramic view of Tiruchirappalli. A flight of steps leads to the Mathrubutheswarar of Thayumanaswami temple, dedicated to Lord Siva where the lingam is a projection of the rock itself. Below the Siva temple are the two Pallava cave temples that have beautiful sculptures of the 6th and 7th centuries. At the foot of the Rock Fort are a tank and a pavilion which are used during the float festival of the temples. Near the tank is the house where Robert Clive lived when he was in Tiruchirappalli and there is an 18th century Church built by Reverend Schwartz of Denmark.
The Rock fort Hillock is said to be 230 crore years old. The materials like Quartz used in glass making and felspar used in ceramic are found in this Rock formation.