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.
Please note it can be very windy at Castle Island, so dress appropriately for prevailing weather conditions. From the parking lot, walk to the left of Fort Independence. As you reach the ocean, there is a fishing pier that can be very crowded during summer, and when certain fish species are being chased into the harbor.