Duisburg was first settled by the Romans in the 5th century. The first mention in written form was in 883, when the town was sacked by Vikings cruising the Rhine river. Originally Duisburg was located directly on the Rhine, but about 1200 the river moved its bed. The borough of Ruhrort was founded in order to establish a new harbour on the mouth of the Ruhr river. Today the harbour of Duisburg is one of the largest inland ports of Germany; the city is also well-known for coal mining and steel industry, although most collieries are closed now.