Hollow cylinder you can walk on the inside of?

[Darth_Biomech]

As far as objects with physics. You can.
You just need to enable physics only when the character is close and disable them as the object’s rotation tilts past its tipping point.
you can actually calculate this with basic physics math. If you know the object size (bounds), its local center of gravity, you can determine at which angle of incline the simulation would tip the object over. I would say to turn it off about 10deg. Before the tipping point is mathematically reached to be on the safe side.
though, you should be aware that the rotation of the base may impart extra force to the math.

Would that fly for barrels or balls though? Those will begin to roll way before the10 degrees angles is reached.
Thanks for ther link!