The underground "city" is a collection of tunnels, metro stations, underground shopping malls, hotels and office towers that are connected together. They are three major "neighbourhoods" in the underground city :

1. The first section starts at McGill metro station (or the Bay store to be more precise) on an east-west axis and run though the Place de la Cathedrale shopping center, Eaton and the Eaton Center shopping center, the Royal Trust Place shopping center, Simpson's (only open during shopping hours, the store itself is closed for the moment) and finally the Cours Mont-Royal (it was an hotel but it has been renovated into a ... shopping center).

2. The second set of tunnels is between Windsor train station (the building that looks like a castle on the corner of Peel and de la Gauchetière), the Gare Centrale (central train station), Place Bonaventure (shopping and exhibition halls, Bonaventure metro station), 1001 de la Gauchetière (there's a year-round indoor ice rink) and Place Ville-Marie (the cross shaped building with a sweeping light on top that you can see for miles at night).

   The Place Ville-Marie has recently been connected by a tunnel with the Eaton Center (if you go from the Eaton center, the entrance is at the restaurant level (basement)).

3. The third set of tunnels starts from the Place des Arts (theater, concert halls, Musée d'Art Contemporain, Place-des-Arts metro station), then goes under Ste-Catherine street to the Complexe Desjardins (office towers, shopping mall, movie theaters, food court), then to the Complexe Guy-Favreau (office tower, gorgeous gardens, Chinatown), then to the Palais des Congrès (congress hall, Place d'Armes metro station) and finally old Montreal. This section of the underground is on a north-south axis. There are small exhibitions (and sometimes interesting) at the Complexe Desjardins and Complexe Guy-Favreau (altough less interesting).

There are also underground "islands", ie. isolated sets of passageways that are not connected to other parts of the underground :

• La Cité appartment complex : there's the Hotel du Parc, the Cinema du Parc (a repertory movie house), a small food court and various stores, the Place du Parc office tower, the La Cité's gym, etc.
• Berri-UQAM metro station : there's the main Université du Québec à Montréal (UQAM) campus, the Place Dupuis and Radisson Hotel, the Palais du Commerce and the Tazmahal indoor rollerblading rink, the Voyageur Bus terminal, etc.
• Square Victoria metro station : there's the Centre de commerce mondial (World trade center) and the Inter-Continental Hotel, the Bourse de Montreal (stock exchange), etc. /li>
• Atwater metro station : AlexisNihon plaza, Westmount square, etc.
• Sherbrooke metro station with its Holiday Inn Metro Center and the Institut d'Hotellerie.

Most tunnels have small shops and restaurants and are usually well marked so you can find your way easily (but not always). They have recently came up with a unified marking system to give directions in the underground but it has not yet caught up everywhere. The signs are suppose to be in purple. The tunnels are also well marked on the transit map available at metro stations.

There are six hotels connected to these tunnels as are many shopping malls, office towers, movie theaters, restaurants, etc.. But all in all there's not much to see there (unless you like shopping). There's the novelty of walking all this way underground and sometimes it's a quick way to walk through some parts downtown. It's also cool in the summer and warm in winter, and it never rains... But it can be interesting if you like exploring, shopping or if you are the only person on earth that never saw a shopping mall....

Note that the access is sometimes limited to store opening hours (Eaton's, Simpson's) or limited to subway opening hours. (see end of the list for those hours).

Metro stations :

McGill and Peel (for the first section)

Bonaventure (for the second section)

Place-des-Arts and Place d'Armes (for the third section)