One of the most interesting places to visit is a spot in the middle of the Sacsayhuaman, Q’enko, Tambomachay area alongside the Pisac highway. The only signs say that Zona X is closed for construction, but there hasn’t been anything happening there in a long time. Only a small building usually occupied by a single worker to keep people out.
I’m guessing the area is closed because it is basically a somewhat dangerous place with lots of deep caves and tunnels and places where thieves can easily take advantage of unwary tourists.
I visited way back in November, 2018 with my two friends, Jesse and Ashley. We had hiked above Tambomachay and, in coming back down, stumbled upon the site. Fortunately there was no one guarding the site at all so we had the place to ourselves for a couple of hours.
I certainly wouldn’t recommend breaking the rules and sneaking in. (We honestly didn’t know it was closed as there were no signs and no one appeared to be around.) If it is every opened again, I strongly recommend going as it is a fascinating maze through a very large rock formation where you could spend a lot of time exploring.
It is a wonderfully mysterious place with an abundance of carvings. Almost no one knows about the site and even fewer visit giving it an aura of mystery unlike anywhere else close to Cusco.