The tower of the Old Post Office Pavilion offers unbeatable views of Federal Triangle, the Washington Monument and the Mall. (Fritz Hahn/The Washington Post)

So where to take guests who want to see Washington from above, or locals who want to take in the city in a different way?

The tower of the Old Post Office Pavilion, right on Pennsylvania Avenue NW.

Today’s Weekend Section has everything you need to know about visiting the tower, which offers an observation deck 270 feet above the city that is reached by taking two separate elevators. The best part: Visiting is free, and no advance tickets are required.