Rotterdam is the second-largest city in the Netherlands and one of the largest ports in the world. The city dates back to 1270, when a dam was constructed on the Rotte River. Since then Rotterdam has grown into a major international business centre. Its strategic location on the North Sea and at the heart of a massive rail, road, air and inland waterway distribution system is the reason that Rotterdam is often called a Mainport or Gateway to Europe. Rotterdam is also known for its modern architecture, with landmarks such as Piet Blom’s cube houses (1984) or the Erasmus Bridge (1996).