Which structure currently operates as a "virtual fence:"  Boarder Wall or Mexico-United States Barrier?
Mexico–United States barrier The Mexico–United States barrier is a series of walls and fences along the Mexico–United States border aimed at preventing illegal crossings from Mexico into the United States. The barrier is not one continuous structure, but a grouping of relatively short physical walls, secured in between with a "virtual fence" which includes a system of sensors and cameras monitored by the United States Border Patrol. As of January 2009, U.S. Customs and Border Protection reported that it had more than 580 mi of barriers in place. The total length of the continental border is 1,989 mi .
Punta Dúngeness Punta Dúngeness is a headland at the eastern entrance of the Strait of Magellan on its north shore, opposite Cabo del Espiritu Santo in Tierra del Fuego. West of the Punta Dungeness lies the Bahía Posesión. Punta Dungeness marks the border between Chile and Argentina, and according to the Treaty of Peace and Friendship of 1984 between Chile and Argentina the line between Punta Dungeness and Cabo del Espiritu Santo marks the limits of each country's territorial waters. It is the southernmost point on the mainland of Argentina, and the easternmost point on the mainland of Chile. There is a lighthouse on the Chilean side.