Frankfurt Airport Visitor Terrace
The Visitors’ Terrace is one of the main attractions at Frankfurt Airport and a popular place to go for outings. It is located in the presecurity part of Terminal 2 and gives visitors a spectacular view of the apron and planes landing and taking off on the runways.
You can park in Terminal 2, and the visit is completely free. The employees are friendly and helpful, and one can visit without reservation or prebooking online.
Alternatively, there are also bus tours with various routes that go around the airport and explain where different things are, for example the fire house, luggage belts, etc...