A wooden watchtower has been rebuilt near Rainau-Schwabsberg, a bit west of the gate at Dalkingen. You can easily see it from the road that leads from Aalen to Ellwangen. In front of the tower is a low palisade. The original tower was erected in c.165 CE, was made of wood, and had three floors.
The upper level probably served as armory. From the balcony, fire and smoke signals could be given to forts in the neighborhood, like Rainau-Buch. The middle level was used a sleeping room and contained the entrance; and downstairs was a cellar.
The first stone towers were probably erected in the early third century. On the picture above to the right, you can see the remains of the successor of the wooden tower above. In fact you can see the foundation of two towers: the upper one stands on the remains of an older foundation.
To the southwest of Rainau was the limes fort of Aalen, which has a nice Limes Museum that supplements the monuments near Rainau.