Fort Margherita was built by James Brooke to guard the entrance to the port. It was completed in 1879, although the numbers over the main gate say 1880. Although the fort was meant to protect Kuching from invasion, the fort was never fired on until World War II, when the Japanese attempted to bomb it, and missed.
The fort consists of a square tower which adjoins an eight-sided redout with cannon ports and an elevated walkway within crenelated walls. The building is now supposedly a police museum, although there were no exhibits in evidence when I visited in March 2011.
The fort is open daily from 9:00 am to 4:30 pm. Admission is free, but there is a fee for taking photos.
To reach Fort Margherita, take a tambang from the landing across the river to the pier just below the fort. There are signs directing you most of the way to the fort, but it's easy to miss the last turning behind the Sarawak legislative complex to reach it.