Panama occupies the central part of the Isthmus of Panama, a narrow bridge of land connecting North and South America. This unique position makes it one of the few transcontinental countries in the Americas. The Panama Canal, completed in 1914, is a 51-mile artificial waterway that connects the Atlantic Ocean (via the Caribbean Sea) to the Pacific Ocean. Before the canal, ships had to navigate the dangerous Drake Passage or Strait of Magellan at the southern tip of South America. The canal uses a system of locks to lift ships 26 meters above sea level to Gatun Lake. Panama's geography is largely mountainous, with two main ranges: the Tabasará Mountains and the San Blas Mountains. It is also home to over 500 rivers. The country is a biodiversity hotspot, containing more bird species than the United States and Canada combined. Panama City, the capital, is the only capital in the world that has a rain forest within its city limits.