{{Dablink|This article is about a London Underground line, for a district line st The District line is a line of the London Underground, coloured green on the Tube map. It is a "sub-surface" line, running through the central area in shallow cut-and-cover tunnels. It is the busiest of the sub-surface lines and the third busiest overall on the Underground network. Out of the 60 stations served, 25 are underground. Two of the four (Richmond and Wimbledon) western branches of the route are also the only lines across the entire network to cross the Thames by bridge and not by tunnel. Although the District line is only the fourth longest line on the network, it serves more stations than any other line.