Those are clearly arches, and they could be a gate. If so, then what they're the gate of, I couldn't say, but if it was a camp it was obviously a permentent one, and these usually
had a village or town (vicus) grow up outside. Depending on the size of the camp, if thart's what it was, you may well have found the source of the audience!
On the other hand, if they're
part of an aqueduct, you'd have to explain why the design of the arches changes; you've got two similar arches, and to the right the pillar of a third, much higher one. An aqueduct would be supplying water to somewhere, and an elaborate
stone one, very difficult and expensive to build, would imply the presence of a major city. Again,. you've probably found your audience, unless it's miles away.
Alternatively, could they be
medieval?