In On the Undergorund, players compete to build the most valuable and convenient transportation network in London or Berlin. Each player controls 2-4 different lines, depending on the number of players.

At the beginning of each turn, 4 Destination cards are facing up, corresponding to stations on the map.

A player's turn consists of taking four actions, followed by the Passneger's movement.

Each action is either building track by placing one Track token, or taking a Branch tile.

After the player's turn, the Passenger token is moved along built lines, avoiding empty track spaces as much as possible in order to reach 1 or 2 of the 4 available Destination stations.

The Destination cards corresponding to the visited stations are then replaced by new ones, and then play passes to the next player in clockwise order.

Players score points in two ways:

- By building track and connectcing their lines to varioud types of stations, by building a cirular line (London), or by collecting Landmark tiles (Berlin).

- By having the Passenger use their lines when moving.

The game is over after all Destination cards have been drawn and all players have taken the same number of turns.