The Semmering railway, which was constructed between 1848 and 1854, holds the distinction of being the first railway to traverse the Alps, and has been commonly referred to as the world's first true mountain railway. The historic significance of this traditional route is such that it has been nominated as a World Heritage Site by UNESCO. By the turn of the 21st century, a total of 70,000 goods and passenger trains were reportedly being run through the Semmering railway during each year, it is one of the busiest routes in Austria.