I cant really name one thing in particular as there are so many different things to do.
I enjoyed the walks the scenery, the people the Buildings everything really.
Its a place you have to see to be able to understand what is unique about Altenahr, for example have you ever seen an eagle in real life?
We did on a couple of occasions,also Red deer.
Its a place you have to explore,there is a ruined castle (at the top of the picture),viewing points,The devils Hole to name a few.
Fondest memory: The Scenery and the Wine.
The hills surrounding Altenahr are very scenic, easy to climb to panaramic views, and lead on to extensive walks around the hills, vineyards and other villages (part of the Rotweinstasse). There is a big map on the notice board by the station/bridge showing the different walks
The first and easiest being the view from Berg Are, the ruined castle above Altenahr. The view from just below the ruins is spectacular - take a camera. I walked up at 06:00 one morning (approx 20-30mins walk alongwide wooded sloped paths, starting from the RatHaus) and saw a woodpecker pecking which made my day. The other walks and milestones along the Rotweinstasse start from here and are clearly marked.
The second must-do walk is up to the White Cross & "hole in the Rock" above the village. Start by walking between the river and the station. The riverside path leads to a tunnel underneath the tracks and from there a 20-30min walk along slate stepped paths to several vantage points. Again there are further walks from these points. The cross is a nice place to come at sunset