Chesapeake Bay, inlet of the Atlantic Ocean, c.200 mi (320 km) long, from 3 to 30 mi (4.8–48 km) wide, and 3,237 sq mi (8,384 sq km), separating the Delmarva Peninsula from mainland Maryland. and Virginia. The drowned estuary of the Susquehanna River, formed in an ancient meteorite impact zone, the bay is fed by rivers including the Potomac, Rappahannock, Pocomoke, and James. It is entered from the Atlantic Ocean through a 12-mi-wide (19-km) gap between Capes Henry and Charles, Va.; the Chesapeake Bay Bridge-Tunnel crosses its mouth, and the Chesapeake Bay Bridge crosses the upper bay. Part of the Intracoastal Waterway, the bay is linked with the Delaware River and Bay by the Chesapeake and Delaware Canal. Baltimore is the largest city and main port on the bay; the Norfolk–Hampton Roads region of Virginia is a key naval complex. The bay's famous fisheries (oysters, crabs, etc.) have declined as residential and commercial development around it have increased; various projects and interstate agreements seek to reverse this trend. A 35-million-year-old impact crater, c.50 mi (85 km) wide, underlies the lower bay. The English colonist John Smith explored and charted Chesapeake Bay in 1608.