Believe it or not, these glass slabs are working speakers

When thinking about a "glass speaker," you probably conjure up images of it being see-through so that you can see all the equipment inside. Well, this isn't like that. The glass on these speakers play a big part in producing 360° of sound.
Pictured up above is the Floe series by Greensound Technologies. The two glass towers stand over four feet tall and weigh 80 pounds each — so still pretty hefty — but don't have all the bits you're used to when it comes to speakers, as you can plainly see.

So, how do they work? Well, the units you see at the base of each speaker vibrate, and the different areas of the glass slabs are designed to produces different frequencies of sounds. In short... magic? As mentioned before, the speakers crank out a full 360° of noise.
The other mystery here is the price, though they should be currently available. You'll just have to hit up Greensound if you're interested.