People in the Netherlands are brainstorming about the feasability to construct a 2000m mountain, the kind with snow on the top for skying and other sports.
This is not an art project, but not yet a commercial project either.
It would be a man-made construction for business and residential purposes, so I guess it's a skyscraper. Some proposals even call for a hollow mountain with shops, sports halls, etc, inside, just like inside a regular skyscraper.
Their website (currently only in Dutch, but with some artist renderings): www.diebergkomter.nl
(url translation: "that mountain will come").