Random Roman Watchtower
When I visited Xanten in 2010, I rented a bicycyle - you can get them everyhwere in the area and there are lots of special cycle lanes - for one day to get to some interesting places, among them the amphitheatre at Birten. I then cycled along the Rhine for a bit and took a turn along a lake.
'South Lake' near Xanten
Where I found this. Well, I had seen a few of those
along the Hadrians's Wall and the Limes and could make a good guess what the foundations were. There also was a sign telling people. My compagnion for a day in front of the foundationas of a Roman watch tower
A Roman watchtower, 5 km from the former fort of Castra Vetera (the few remains of which are now buried beneath a grain field on the slope of Fürstenberg Hill). There must have been a chain of those along the Rhine - or rather, where the Rhine had been in Augustean times; its meanders have shifted a bit. Closer view
The foundations of 4 x 4 metres are made of greywacke and mortar and are sufficient to support a wooden or half timbered construction of several storeys. There's no mention that this tower had ever been reconstructed all in stone like some of those at the Hadrian's Wall and Limes.Different angle
Access would have been by a ladder to the second storey. The lower storey was used to store provisions, the middle one for living quarters, and the highest one was the actual lookout. Since the land around Xanten is rather flat, you could see far on a clear day. View from the other side of the lake towards Xanten with the cathedral
I cycled along both the south and north lakes - artificial lakes made for recreational purposes, but very quiet on a dreary day like when I was there - and returned to Xanten in late afternoon. Though the weather wasn't bad for cycling at all; not too much wind and no rain.