I took the train to Maienfeld, and then the bus to St. Lutzisteig. From there I started my ascend towards Fläscher Fürggli. The Fläscher Tal has three beautiful lakes. And I headed then to Älpli, where is a cable car going down to Malans. You should book in advance, or hoping for a free space. Then you have to talk to the guys at the restaurant.
That's about 1800 m elevation up, and 700 m down and 15 km long.