Abridged History of the 10th Age
The Rhun cuts down through Blackwood Forest, originating in the Teralian funerary capital of Acerdus. It is a swift-flowing river, and very difficult to cross. Luckily, there is a place where it dives under ground, at the North-mount in Northmount Abbey. The river there enters the hill beneath the fortified abbey by means of many small holes and tunnels and passes out on the other side. Most travelers cross the river by this means.