In under an hour driving from Garmisch Germany towards Innsbruck, Austria is the highline 179 & Ehrenberg castle ruins in Reutte, Austria. Highline 179 is the longest Tibet-style pedestrian suspension bridge in the Guinness Book of World Records as of 2014 running 406 meters long between the Ehrenberg Ruins and Fort Claudia and over 100 meters high. There is nothing in the town there, a tiny museum and one restaurant and church. The information center there is where you get the ticket to enter to cross the bridge for under 10 euros. There is no cost to hike up to the castles and forts. The hike to the bridge entrance and first castle ruins Burgenwelten Ehrenberg is really steep but the path is marked and frequently traveled so easy to follow.
Continuing from there is a second hike to the Schlosskopf, the highest fortress in Austria. It takes about 2 hours round trip if you hike fast, and is much more steep and difficult through uneven grounds up the mountain. The weather was good for us that day, and my legs were definitely sore the next day from the steep climb. The views are completely worth it.