In the 12th century, the republic built a large national shipyard that is now known as the Venetian Arsenal. Building new and powerful fleets, the republic took control over the eastern Mediterranean. The first exchange business in the world was started in Venezia, to support merchants from all over Europe. The Venetians also gained extensive trading privileges in the Byzantine Empire, and their ships often provided the Empire with a navy. In 1182 there was an anti-Catholic massacre by the Orthodox Christian population of Constantinople, with the Venetians as the main targets.