The town gate is always located at the top of a town, directly above the bus stop. It is actually a separate area located just outside of town, and it performs a number of town functions.

While still in the town, the town gate is large and obviously gate-like in appearance. This appearance in Animal Crossing: City can actually take one of a few forms (seen below) which is determined on town creation and does not change. All town gate appearances have a town flag on the right-hand side. The gate's lights turn on at 6:00 PM.

Copper (left) and Booker (right).

Inside the gate area itself, Copper and Booker stand guard. Copper's demeanor is that of a dutiful guard whereas Booker's nature is more laid back. Each performs different roles.

Talking to Copper primarily allows you to interact with players of other towns: Either by visiting other peoples towns over Nintendo Wi-Fi Connection, using the DS Suitcase feature or by opening your town gates so someone using Nintendo Wi-Fi Connection can enter your town.

Booker's functions are more to do with your town. Speaking to Booker, you can find out if any special characters are visiting your town. You can also check your town's lost and found (which items are placed in if, for example, they were placed outside and a house was built over them). Finally, you can change your town flag with Booker by giving him one of your designs. The previous flag can either be discarded or switched with the design you choose to use as the town flag. The default flag is made by Wendell.