Tourists are drawn to Switzerland's diverse landscape as well as the available activities, which take advantage of the Alpine climate and landscapes, in particular skiing and mountaineering, but also due to the many old town centers, with their historic buildings that often preserve parts of their medieval fortifications, and Roman sites. Switzerland is also popular for tourism-oriented railways.
As of 2016,[update] tourism accounted for an estimated 2.6% (CHF 16.8 billion) of Switzerland's GDP, compared to 2.6% (CHF 12.8 billion) in 2001.[1]