Frankfurt's zoo, founded in 1858, is the second-oldest in Germany after Berlin and one of the most respected scientifically — its post-war director Bernhard Grzimek was a pioneer of African wildlife conservation and his Frankfurt Zoological Society still runs serious work in the Serengeti, Manu and Gunung Leuser. The zoo itself is compact (only 13 hectares, on a city-centre site between Bornheim and Ostend), which has forced creative animal-housing — the bat cave, the cat jungle, and the Grzimek House (a darkened building with nocturnal animals) are among the best-designed exhibits in any European zoo.
A handful of the older enclosures still look small by modern standards, but ongoing rebuilds (most recently the new ape complex) have brought most of the zoo up to current best practice. Open daily 9am to 5pm (later in summer); entry around 14 euros for adults. Easy to combine with a walk down Berger Strasse in Bornheim.