After the destruction of Koneswaram Temple, Fort Frederick was built by Potrugese in 1624 by the Portugese, and later re-engineered and renovated by the Dutch in 1665. It's also where the Dutch first landed on the Island. The fort is on the highest grounds of Trincomalee and guards the entrance to the Konamalai cape; you will be passing its main entrance while visiting Koneswaram Temple, which was guarded by old cannons. It’s loved by many tourists as a place to stroll around. You’d see spotted deers in the area who live freely.
Originally the fort was built in a triangular shape with three bastions at the three points and was called Fort of Triquillimale, the most important bastion defending the bay was called “Santa Cruz” and was equipped with guns captured from a Danish fleet ship. It was built after the destruction of Koneswaram Temple, stone pillars, stone carvings of the temple were used in the construction. The fort was used as a military base against the invading Dutch armies during the Dutch-Portugese wars.
In 1639 the fort was captured by a Dutch fleet under the command of Admiral Westerwold. After identifying the emerging threats from the British and French, the Dutch completely dismantled the fort and rebuilt it in 1665. They also renamed it as “Fort Frederick”. The military bases didn't get to stand strong for more than twelve years, and the French captured it in 1672. In 1795 it was again taken over by the British. The fort still houses a detachment of the Gajaba Regiment of Sri Lanka Army, however is accessible by visitors.