Wetzler to Giesen - by bike

My goal is to eventually cycle the full length of the Lahn River (245km).  Today I did just the short section from Wetzlar to Giesen (18km)- caught the train to Wetzlar then caught the train back to Marburg after cycling to Giesen.  It was a flat ride but for some reason seemed a lot longer - maybe it was the hot humid day, but I devoured a plate of ice cream once I got myself back up the hill and home again.  I enjoy cycling by myself at my own pace.  I have now completed about 1/3 of the distance.