Palmengarten, Grüneburgpark, and the Botanical Garden form the largest inner-city green area in Frankfurt. Combining these adjoining green spaces makes for a lovely run of decent length. The restored 54-acre Palmengarten is an important botanical garden. A loop around here is about 1 km.
Then head over to neighboring Grüneburgpark, which at nearly 60 acres, features Botanic gardens, an open-air theatre & Korean Garden, and sizeable lawns in the former castle grounds of Rothschild family. Enjoy the many paths, or loop around the perimeter for about 2 km. The run concludes with a quick jaunt over to the well-regarded Goethe University, where you can enjoy some of the campus paths and gardens.
A tour of these three neighboring spaces is about 6.5 km (4 miles), or form your own route!