The remains of Kalutara Fort are located at the mouth of the Kalu Ganga, right beside the Gangatilaka Vihara. The Portuguese originally built a fortification here in 1622, which the Dutch took in 1659 and later strengthened. The British arrived in 1796 and used the position until they no longer needed it.
Very little of the original structure survives above ground — the site has been built over repeatedly and the Buddhist temple now occupies the most prominent position. What remains is mostly foundation stonework and a few earthworks that are identifiable to those who know what to look for. The site is more interesting historically than visually, but it provides context for understanding why Kalutara developed as a significant coastal settlement.
The fort's position at the river mouth made it the critical control point for the interior. Cinnamon brought down from the Sabaraga muwa hills passed through here before it could reach the coast and the ships waiting offshore.