For the past seven years, the staff at Turnstile Tours has been offering two-hour bus and bicycle tours of the typically off-limits Brooklyn Navy Yard, a sprawling 300-acre property that includes a whole lot more than woodworking studios and the Brooklyn Grange. For starters, there's an 1856 eagle-topped monument tucked away there, commemorating the Battle of the Barrier Forts, an assault led by the U.S. Navy against Qing Dynasty citadels on China's Pearl River, during the Second Opium War. Who could forget!

Photographer Tod Seelie recently trailed Turnstiles tour guide Andrew Gustafson on a special New York Obscura Society tour that covered landmarks architectural, ecological, and historical. Stops included the austere marble Naval Hospital, which operated from 1838 to 1948, and is one of the yard's last remaining unrestored spots—besides Admiral's Row, which is being demolished, save two buildings. The hospital's 24-acre plot also includes quaint surgeon's quarters, decked out with creeping vines.

Gustafson showed off the Naval Motion Picture exchange, as well, which lent film reels out to sailors during World War II.

Amidst these historical landmarks, the New York Harbor School is working on an oyster restoration project at the Navy Yard barge basin—raising one billion oysters to maturity and depositing them around NYC waterways. And no Brooklyn Navy Yard tour is complete without a trip to the dry dock. Built in 1851, the dock still functions as a site for commercial ship repair.

All Brooklyn Navy Yard tours are hosted in conjunction with BLDG 92, the yard's exhibition center and home to "Brooklyn Navy Yard: Past, Present, and Future." Group tours—$30 by bus and $24 by bike—take place on Saturdays and Sundays from 2:00 to 4:00.

BLDG 92 is located at 63 Flushing Avenue at Carlton Avenue in Fort Greene (718-907-5992;