at 99 million passenger journeys in 2004, but has experienced a recent (2013) revival due to infrastructure improvements and partial privatisation of lines, accounting for 45% of all passenger and freight movements in the country. Bucharest Metro, the only underground railway system, was opened in 1979 and measures with an average ridership in 2007 of 600,000 passengers during the workweek in the country. There are sixteen international commercial airports in service today. Over 12.8 million passengers flew through Bucharest's Henri Coandă International Airport in 2017. Romania is a net exporter of electrical energy and is 52nd worldwide in terms of consumption of electric energy. Around a third of the produced energy comes from renewable sources, mostly as hydroelectric power. In 2015, the main sources were coal (28%), hydroelectric (30%), nuclear (18%), and hydrocarbons (14%). It has one of the largest refining capacities in Eastern Europe, even though oil and natural gas production has been decreasing for more than a decade. With one of the largest reserves of crude oil and shale gas in Europe it is among the most energy-independent countries in the European Union, and is looking to expand its nuclear power plant at Cernavodă further. There were almost 18.3 million connections to the Internet in June 2014. According to Bloomberg, in 2013 Romania ranked fifth in the world, and according to The Independent, it ranks number one in Europe at Internet speeds, with Timișoara ranked among the highest in the world. Tourism Tourism is a significant contributor to the Romanian economy, generating around 5% of GDP. The number of tourists has been rising steadily, reaching 9.33 million foreign tourists in 2016, according to the Worldbank. Tourism in Romania attracted €400 million in investments in 2005. More than 60% of the foreign visitors in 2007 were from other EU countries. The popular summer attractions of Mamaia and other Black Sea Resorts attracted 1.3 million tourists in 2009. Most popular skiing resorts are along the Valea Prahovei and in Poiana Brașov. Castles, fortifications, or strongholds as well as preserved medieval Transylvanian cities or towns such as Cluj-Napoca, Sibiu, Brașov, Alba Iulia, Baia Mare, Bistrița, Mediaș, Cisnădie, Sebeș, or Sighișoara also attract a large number of tourists. Bran Castle, near Brașov, is one of the most famous attractions in Romania, drawing hundreds of thousands of tourists every year as it is often advertised as being Dracula's Castle. Rural tourism, focusing on