For an easy hike across some of the nicer farmland north of Frankfurt, there is the Monastery of Ilbenstadt. The monastery complex is mostly preserved and features a remarkable late Staufen Romanesque church and a Rococo gatehouse, hinting at the centuries of prosperity enjoyed by the monks here. Behind the monastery is a nicely preserved agricultural complex from the 19th century.
The Red Moor is an ancient wetland in the highlands of the Rhön. Though much of it was drained or harvested for peat, today, it is a nice glimpse of the primeval landscapes of Europe. Including ancient deep ponds or "eyes of the moor," which served as cult sites for worship through to the end of the middle ages.
The Vogelsberg is a region in Upper Hessen known for its rolling and forested landscape. Much like the Odenwald and Westerwald, it's a mixture of small villages, forests, and agricultural land. This hike takes you up through this landscape to a highland moor, an ancient wetland with a unique natural landscape.
This hike takes you above the town of Boppard in the Middle Rhine Valley. Starting on the opposite bank, though, we first visit the Sterrenberg Castle ruins before descending to the river again with beautiful views of Boppard along the way. Optionally, once across the river, you head up above the Rhine again for some epic views of the famous horseshoe bend in the river.
The Hubertus Viaduct is one of only a handful of those glorious 19th-century railway bridges that both a) survived WW2 and the post-war reconstruction and b) remain in service. Though the viaduct is not perhaps a common image in the Middle-Rhine Valley, it often appears in other media, as it is one of only two easily photographed operational viaducts in Germany.