You’re not going to hear anyone say this about the Roman Coliseums and attached ruins.
I went to college with a, well, it was a D&D-playing time, so, a bunch of dorks, including me. One guy who lived somewhere down the hall but hung out with my next-room neighbors had led a posh childhood, and claimed to have found "authentic Roman dice" in a crack in the floor in the Coliseum. Tour guides at ancient sites are, of course, notorious for 'salting' the areas where the tourists are heading. At Giza, tour guides were known for sending their marks on hunts for "fossil wheat" that sure enough turned up in little nooks and crannies. Compared with Pompeii, the Coliseum has nothing to steal, it's been pretty exposed and stripped clean, standing out in the open since it was constructed. Old paintings of 200-300 years ago show trees growing on upper rim.
Also, the construction is that of barrel vaults which start large on the outside and converge to a smaller size (hor. and vert.), making the structure crazy strong, ridiculously hard to knock down. Just leaning on a wall probably won't do much, even if one has brought along a pet elephant.