London The Underground

CARNET. A carnet is a book of 10 singles, available only for a Tube journey starting and finishing in Zone 1; they cannot be used as extensions, nor can you purchase extensions for them. Each ticket must be validated at the station before you use it; failure to do so counts as fare evasion. Purchasing a carnet is cheaper than buying individual singles, but unless you plan to do a lot of walking, a Travelcard is definitely better. See www.tfl.gov.uk.

NAVIGATING THE SYSTEM. Color-coding makes navigating the 12 lines a breeze. Platforms are labeled by line name and general direction, and most have a digital sign indicating the minutes until the next train arrives. If you are traveling on one of the lines that splits into two or more branches, check the platform indicators or the front of the train.

HOURS OF OPERATION. The Tube runs daily from approximately 5:30am to midnight, giving clubbers that extra incentive to party till dawn. The exact time of the first and last train from each station should be posted in the ticket hall; check if you think you’ll be taking the Tube any time after 11:30pm. Trains run less frequently early mornings, late nights, and Sundays.

TICKETS. You can buy tickets from ticket counters or machines in all stations. Tickets must be purchased at the start of a journey and are valid only for the day of purchase (including round-trip tickets, but excluding carnets). Keep your ticket for the entire journey; it will be checked on the way out and may be checked at any time. There’s a £20 on-the-spot fine for traveling without a valid ticket.