Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
Greenwood Tunnel
The Greenwood Tunnel is a historic railroad tunnel constructed in 1853 by Claudius Crozet during the construction of the Blue Ridge Railroad. The tunnel was the easternmost tunnel in a series of four tunnels used to cross the Blue Ridge Mountains of Virginia. Located near Greenwood in Albemarle County, Virginia, the tunnel was used by the Chesapeake and Ohio Railway (C&O) until its abandonment in 1944. The tunnel still exists, though sealed, next to the old C&O line, now owned by CSX Transportation and leased to the Buckingham Branch Railroad, which runs through a cut bypassing the old tunnel.