Peering through Teufelsloch (Devil-hole) you can see a castle's ruins. The structure began its life in 1244 and had a series of renovations through the 1400's. While the ruins of "Burg Are" suggest immense power and control over the valley & its inhabitants for hundreds of years the real power is the geology that belies the fact that you are walking on an ocean bottom millions of years older. The trail (actually 3 distinct hikes) is delightful in that it winds itself around the hills, about one half through the town about a third up the side of the hill. At the ruines a wonderful view of the local villages, the river & railway line can be enjoyed (along with a castle wine --& if your timing is right: a guided vineyard tour).
After a well-deserved pause descend to the Langfigtal (designated as a nature reserve "Ahrschleife in Altenahr") on the other side of the Ahr. Its 205-acres preservation is a river landscape w/its rock formations of keen scientific & natural historical interest -- as well as habitat for rare endangered birds & wild plants. It's an ideal spot to cool down and even take a dip in the river -- as many of the locals do. The Langfigtal trail is wheel-chair accessible, pet-friendly and has numerous well-positioned benches -- though portions of this excursion come with a physical price. You're rarely walking on level ground; it's either up or down so bring along ample fluids. Parking nearby is free & plentiful. The train station is convenient.