Go on top of the Feldberg mountain, the highest mountain of the Taunus. Take a train from Frankfurt central to Königsstein and then go to the main bus place (Parkstraße). Busses via Feldberg depart every 2 hours. Get on top of the observation tower at the Feldberg. If it's cold, have a hot chocolate with cream (Heiße Schokolade mit Sahne) at the tower's kiosk.
