The River Lum is a river flowing through mostly Misthalin and the Wilderness, moving north-to-south. It is the second longest river in RuneScape. Its source is in the Wilderness. It runs as an underground stream until it emerges just north of the Wilderness border. It filters out to the sea on the Misthalinian-Kharidian border. The town of Lumbridge is named after the river.
Travelling the river