Utrecht was the medieval capital of the northern Low Countries, where it was the most populous city until economic growth in the later Middle Ages turned centres of trade like Amsterdam into boomtowns. Ottonian and Salian emperors frequently visited Utrecht. Two of them, Conrad II and Henry V, died there. 1 Most importantly, Utrecht was the seat of a bishop and, therefore, a religious centre. This religious importance explains the presence of two military orders: both the Hospitallers and the Teutonic Order had their regional headquarters in Utrecht.