Fort William is situated on the Eastern banks of River Hooghly and it was named after King William III of England. The Maidan opposite the fort is the largest urban park in the city. There are two Fort Williams here, the new and the old and the old fort was originally built in 1696 by the British East India Company. Again British built the new fort in Maidan and the constructed was started by Robert Clive in 1758 and completed in 1781. It spreads over an area of 70.9 hectares of land.

The Old Fort is now used as customs house. The new fort has the shape of an irregular octagon and is surrounded by a dry moat about 9 meters deep and 15 meters broad. It has a star front that will defend it from cannon.