You’ll find most major cities have special bus lines that will take you to the most interesting and popular destinations within the city. These are usually not operated by the city but, independent bus and tour operators.
Hop On Hop Off buses in many of major tourists cities. These buses run predetermined circular routes making stops in front of famous landmarks or sights. Let’s say your in Paris and you hop on the bus at the Eiffel Tower and ride it to the Louvre. Hop off, take in the Louvre and when you come out wait for the next bus and hop on. Take it to another location and hop off. You can do this all day and while you’re riding from stop to stop you can a view of Paris and it’s neighborhoods. Free use of Hop On Hop Off buses are included in many of the city cards and passes you may purchase. Some may be limited to just one day’s use but, they are a great way to ride around and take in the sights and sounds of a city.