The Fitchburg Line is a branch of the MBTA Commuter Rail system which runs from Boston's North Station to Fitchburg, Massachusetts. The line is along the tracks of the former Fitchburg Railroad, which was built across northern Massachusetts, United States, in the 1840s. It is one of the more scenic commuter rail lines, passing by Walden Pond between Lincoln and Concord. Weekend service includes a specially equipped seasonal "ski train" to Wachusett Mountain.