The Arlesdale Lake and Mountains Line is a railway line on Toby's Branch Line. The line runs on a mountain, passing a cliff side. Next to it, there is a small ruined castle. At the end of the mountain, there is a line which runs along a large lake. Toby used to work here, but soon the lorries and buses were taking over his work and he was locked up in his old shed at Arlesdale End, until he was bought by Sir Topham Hatt. A few years later, the old lake and mountains line was reopened up and is used for holiday makers and tourist attractions. On occasions, Thomas takes passengers here. 

The line was only seen in the first and third seasons and some songs.