Salzburg is the fourth-largest city in Austria and the capital of the Federal State of Salzburg. Its historic centre (Altstadt) is renowned for its Baroque architecture and is one of the best-preserved city centres north of the Alps, with 27 churches. It was listed as a UNESCO World Heritage Site in 1996. The city has three universities and a large population of students. Tourists also visit Salzburg to tour the historic centre and the scenic Alpine surroundings. Salzburg was the birthplace of the 18th-century composer Wolfgang Amadeus Mozart. In the mid‑20th century, the city was the setting for the musical play and film The Sound of Music.