In the 19th century the Ship Island in Mississippi Gulf Coast was part of extensive costal defense system. Erected on this island Fort Massachusetts was one of many guarding posts in the southern United States. This particular structure has impressive masonry work. Outer walls reach the width of 8 ft/2.5 meters. Arched or vaulted passageways supported the weight of 17 cannons mounted on the top of the structure (to this day remains only one). The fort was intended to withstand a long siege and was designed to have its own water supply. Large cisterns beneath grand level built in order to collect rain water through drains in the wall structure. The entire system still operates today. The soils with grass on the fort top level serves as natural filtration system, making collected water safe to drink.
