Calshot Castle was built in 1540 as part of Henry VIII's chain of coastal defenses. The design of Calshot Castle is essentially a three-story gun tower. It is a small castle, but its importance to the protection of the ports in the Southampton Water exceeds its size many fold. Calshot is sister to the larger Hurst Castle that protects the western end of the Solent.

Around 350 years after the castle was first built it provided significant defensive power during the first and second World Wars. It was of strategic importance to both the Royal Navy (RN) and Royal Air Force (RAF).

The Castle has been associated with the Schneider Trophy air races, and the large hangers that once housed the flying boats of the RAF, now accommodate a wide variety of activity centers.

This is a wonderful site to visit. There are fantastic views of the solent and interesting exhibits to view.