My wife and son worked on an interesting winter project in recent weeks.
They froze balloons filled with colored water, and then pulled off the rubber to reveal astonishing aqua-boulders with striking colors and color patterns. Food coloring is suspended within the ice in all kinds of zany ways.
My wife and son even put little toys inside some of the balloons.
After the balloons froze (which took about two days with mild winter temperatures, and one day during the recent Polar Vortex), my wife and son peeled them like onions, used a sled to remove them from the back-yard prep area, and arranged them alongside the street in front of our house.
My wife thought up this idea on her own, but a quick Google search shows lots of other people doing similar. Fun stuff.
See more photos (and animated GIFs) here.