I’ve said it before and I’ll say it again – dig at your peril in Mainz.
You’re likely to stumble across a Roman boatyard with the remains of 17 canoes. Which need preserving. (And brother, did THAT stuff the city’s budget…)
That was the Hilton extension.
You might also find yourself in the middle of a temple to the Goddess Isis (Nothing to do with that Middle Eastern lot…) when all you want to do is build an underground carpark underneath your covered arcade.
But the vegetation here has the right idea, as did the builders of the 13th C city walls.
The latter stumbled over Roman walls that tracked pretty much where they’d figured on placing their fortifications (Great minds think alike, fools seldom differ…) so they bowled the shonky stuff and just built on top.
800 years later, the vegetation had the same idea.
“Oh look, a convenient wall integrated into a new building. I think we’ll just settle down here…”