The ride to the city from Frankfurt airport is quick and pleasant, if not entirely obvious. Walk outside arrivals, on level 1, to the north side of Terminal 1 and head east until you see overflowing bike racks. Follow the bike signs from there, through the little empty parking area for busses, and onto the red brick path. Pedal through a quiet forest park; emerge through a bit of town and onto the bike path along the river to the city.