Maastricht developed from a Roman settlement to a medieval religious centre. Today, the city is a thriving cultural and regional hub. It became well known through the Maastricht Treaty and as the birthplace of the euro. Maastricht has 1677 national heritage buildings the second highest number in the Netherlands, after Amsterdam. The city is visited by tourists for shopping and recreation, and has a large international student population. The Meuse-Rhine Euroregion is a metropolis with a population of about 3.9 million with several international universities.