>something like Stonehenge could be assembled in a matter of minutes with modern machinery //

I'd visit that, has anyone done it? Would be great to have some of the burial mounds created so you could walk through and see them from the inside too.

You could have a "moving of the stones" festival where people could come and camp and have the opportunity to take part in moving and placing some megaliths. That'd be fun! (Kinda like a Society for Creative Anachronism (SCA) project.)