The Harlon Underground is one of 4 of the major rail networks in Harlon. It currently operates 7 lines, with an 8th under construction. These lines are: Celcius, Circle, District, Hamperton and City, Millenium, Metropolitan, Piccadilly, Queenvic, and the River Line (under construction). Major hubs of the Underground include Stockholm Street and Parliament Square. All lines are automated except for the Queenvic.
The Celcius Line has many different terminals and branches. Typically, trains will go from Epping to North Olympia, however some trains will terminate at Ruislip, Elstree Broadway, Oldbury Park, Heynoult, or Stoneford. This line has many important stops, including Stockholm St, Aldrington, Epping, Stratford, and Sergel's Sq.
The District Line, like the Celcius Line, has many different branches and terminals. Trains terminate at Upminster, Edward Rd, Arena (Olympia), Wimblerton, Sudbury Town, or Elstree Broadway. Important stops on the line include Upminster, Copenhagen Street, Earl's Court, and Parliament Square.
As it's name suggests, the Circle Line loops around Harlon, unlike the other lines on the Underground. Trains make important stops at Aldgate, Parliament Sq, Belton St, North Av, Queen's Cross, and Stockholm St.
The River Line was originally going to be completed, running from Waterloo to Edminton, but due to the work on NH, it has been scrapped. However, it is available to access some of it through Explorer Quests.
The Millennium Line serves many parts of Harlon, with trains running between Belton Street and Stenford Bay. It serves many important parts of Harlon with its stops, including Penrith Central/Riverside, South City Park, Stenford Bay, Parliament Sq, and Sergel's Sq. It was supposed to go to Stanford, but the extension was cancelled for the same reason every other extension was.
The Metropolitan Line is another unfinished and abandoned line on the Underground, which if it had opened, would've been used for easy transfers and shortcuts along numerous lines.
The Queenvic Line is the only line in the entire Underground to be manually operated, and is currently the shortest line on the Underground. The Queenvic currently runs from Queen's Cross to South Avenue, and makes important stops at North Av, Victoria, and Queen's Cross. Anyone who has the Overground License, can operate the train.
The Piccadilly Line is the most recent line on the Underground as of May 2021, and runs from Sudbury Town to Green Park. 2 extensions were originally planned for it: one from Sudbury Town (SB terminal) to Harlon Intl Airport, and another from Green Park (NB terminal), to Cockfosters, however this was scrapped in favor of working on NH.