Occupying the neck of a narrow peninsula, Fort Frederick has been a defensively important site for centuries. A fortress was initially constructed here by the Portuguese in 1623 and later rebuilt by the Dutch. The British took over in 1782 (look out for royal insignias crowning the tunnel-like gateway that pierces the fort’s massively stout walls).
The fortress is used today by the Sri Lankan military, but you're able to explore most of the fort by foot or car.
Assorted cannons and artillery are dotted around the enclave, which also contains a small number of spotted deer grazing under huge banyan trees.
Among the colonnaded colonial-era buildings, the impressive Georgian-style mansion (not open to visitors) is Wellesley House, named after a Duke of Wellington. It dates from the late 1700s. There's also a big standing Buddha statue at the Gokana Temple, from where there are fine views of Trinco and the coastline.