This little fort was built by the founder of Saudi Arabia, King Abdul Aziz, early in the 20th century. It's square-shaped, with a central courtyard and a disused well. At the time of research the fort was in the process of becoming Haql's very first museum, with crates of antiquities waiting in the small rooms where they are due to be displayed. The fort has been painted white and is a nice example of early Saudi defensive architecture.
It's located opposite the police station.