Here's an art installation made by artist Jonathan Schipper featuring a hot tub standing in for the ocean with tons of salt doubling up as sand.

Called the Salt Machine, visitors can build "salt" castles without having to leave the hot tub. The installation is controlled by four cables attached to motorized pulleys and can reach all corners of the gallery.

But where's the fun in building castles if you have to get a machine to do it, right? Check out the video of the machine below: [Jonathan Schipper via designboom]