Yes! It's the latest thing in salt domes!

A huge balloon is the form for this remarkable structure being constructed out of steel-reinforced concrete near Nashville, Ohio. Jason Carroll gave us a tour and even let us take a look inside, which involved crawling through an airlock and feeling it in our ears. When the concrete is hard, the balloon will be deflated and removed. A door will be constructed in the side, and the dome will be ready for use. The whole process takes about three weeks.