A Martello tower is a type of small defensive fort that was built across the British Empire during the 19th century, from the time of the French Revolutionary Wars onwards. Most were for coastal defense.
A Martello tower stands up to 40 feet (12 m) high, with two floors and a typical garrison of one officer and 15–25 men. The round structure and thick solid masonry walls made it resistant to cannon fire, while its height made it an ideal platform for a single heavy artillery piece, mounted on the flat roof and able to traverse over a complete 360 degrees. A few towers had moats or other batteries and works attached for extra defence.