This ancient and historic city houses many buildings going back to the early Middle Ages. Until it was overtaken by Amsterdam in the Dutch Golden age, Utrecht was the most important city in the Netherlands. It was and still is the See of the Archbishop of Utrecht, the most important Catholic leader in the Netherlands. The University of Utrecht is the largest in the Netherlands. One of the unique features of the city is the wharf system in its inner canals. Before the city was fully canalised, parts of the Rhine River flowed through the city center. Most prominent of the historic buildings is the Gothic Cathedral of Saint Martin, the construction of which lasted for almost 200 year, beginning in 1254.