The Charlestown Navy Yard is home to the USS Constitution, the oldest commissioned warship at 215 years old. In July 2013 we could no longer do a self tour below decks, only topside. However, wait for the below decks tour. Old Ironsides id the best deal in Boston, its free. The destroyer Caissin Young is temporarily docked away from the yard while repairs are made to the dry dock in which it is normally located. The only way to see the yard is to the second best deal in the city, the water taxi from the Aquarium wharf to the Navy Yard. A 15 minute ride with the city as a backdrop for only $3.00 for adults. Either take the water taxi back to the waterfront, or walk towards the bridge and walk back through he North End for gelato, wine or whatever.