The city has an extensive green belt. Some of the neighbourhoods constructed after 2000 are densely built up and lack green spaces. There are four principal parks – Borisova gradina in the city centre and the ''Southern'', ''Western'' and ''Northern'' parks. Several smaller parks, among which the Vazrazhdane Park, Zaimov Park, City Garden and the Doctors' Garden, are located in central Sofia. The Vitosha Nature Park (the oldest national park in the Balkans) includes most of Vitosha mountain and covers an area of , with roughly half of it lying within the municipality of Sofia. Vitosha mountain is a popular hiking destination due to its proximity and ease of access via car and public transport. Two functioning cable cars provide year long access from the outskirts of the city. The mountain offers favourable skiing conditions during the winter. During the 1970s and the 1980s multiple ski slopes of varying difficulty were made available. Skiing equipment can be rented and skiing lessons are available. However, due to the bad communication between the private offshore company that runs the resort and Sofia municipality, most of the ski areas have been left to decay in the last 10 years, so that only one chairlift and one slope work.