Finished in 1653 by the British East India Company, the fort has undergone many facelifts. Inside the vast perimeter walls (the ramparts are 18th-century replacements) is now a precinct housing Tamil Nadu's Legislative Assembly & Secretariat, and a smattering of older buildings.
The Fort Museum has displays on Chennai's origins and the fort, and interesting military memorabilia and artwork from colonial times. The 1st-floor portrait gallery of colonial-era VIPs includes a very assured-looking Robert Clive (Clive of India).
Also within the fort is St Mary's Church, completed in 1680, and India's oldest surviving British church, surrounded by even earlier gravestones; Clive was married here. To its right (west) is the neoclassical former Admiralty House (Clive's House).