The remains of the roman Watchtower can be visited
Roman Watchtower 2/25

The Upper Germanic-Rhaetian Limes, with a length of 550 km, from Eining near Regensburg to Rheinbrohl on the Rhine, is the largest archaeological monument in Germany and has been recognized by UNESCO as a World Heritage Site. Limes (Latin: border path/wall) refers to the border fortifications of the Roman Empire, which were erected towards the end of the 1st century AD.
This border was monitored by more than 900 towers, which were built in timber construction during the initial phase, starting around 80 AD. Stone towers followed, which were plastered from 150 AD onwards. Excavations have shown that the white plaster often had incised joints, which were painted in terracotta. This created the impression of beautiful ashlar masonry.
Watchtower 2/25+
A tower site still visible in the terrain today, with two wooden towers and one stone tower.
The square stone tower had a side length of approximately 5.50 m and a wall thickness of only 80 cm. At a distance of about two meters, the tower was surrounded by a shallow ditch, also almost square, which in places was filled with large quantities of burnt debris, wattle and daub, and slate slabs. In the western corner of the tower was a pit 75 cm wide, 1.40 m long, and 2.40 m deep, of unknown purpose. It was filled with the building rubble of the tower. Immediately in front of the stone tower site, the Limes wall and large ditch were interrupted. The foundations of the stone tower are preserved.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Frank Winkelmann / CC BY 3.0 via Wikimedia Commons
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Location: 50.2440, 7.8762