For a small city, Frankfurt has a fair share of sights. Must-sees include a trip up to the top of the Main Tower skyscraper (or, lacking money or time, to the top floor of the Zeilgalerie mall), a stroll from Opernplatz to Konstabler Wache and a peek at the Römerberg. With more time on hand, visit the Städelsches Kunstinstitut museum.