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.[13] 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.