It's freaking cold outside, and depending where you live, it might just be snowing. If you have lots of free time on your hands, and want to make something truly cool, why not go all-out and construct an urban igloo?
Modern Farmer got the inside info on how to make it happen from the good folks at the aptly named Urban Igloo blog, and... ok, it's not exactly easy, but it can be done. This thing could be an all-in-one frigid part-time office, playhouse, and sulky getaway for a little non-familial alone-time.
Apart from the space issue -- a flat area about 2.2m in diameter is required -- forming the bricks themselves seems like the major challenge here. They suggest tightly packing kitty litter bins -- but you'll need 150 individual bricks, and have to let each set for a solid half-hour before starting to build.