Vitamin D -- specifically the form D3 -- is the only vitamin your body makes itself. It's fat-soluble, which means your body stores vitamin D in its adipose tissue -- in its fat. And, if you want to be specific about things, this vitamin is actually a hormone.
Sullivan's Castle Island, South Boston, MA, Est. 1951. Castle Island. Located at the end of Carson Beach, on Pleasure Bay in South Boston, Castle Island is a 22-acre recreation site, and the site of Fort Independence. Castle Island was really an island until several land reclamations through the years extended causeways and eventually roadways.
Fort Independence and Castle Island are on the State and National Registers of Historic Places. Fort Independence is open from Memorial Day to Columbus Day, hours vary. Fort tours are conducted by the Castle Island Association in the summer months and there is interpretive signage for self-guided tours.