Antonov An-225: World's biggest unfinished airplane lies hidden in warehouse

Kiev, Ukraine (CNN) — On the outskirts of Kiev, somewhere between the city's Nyvky and Sviatoshyn metro stations, sits a drab industrial building that you could drive past a thousand times without guessing it contains an extraordinary secret.

Inside can be found the unfinished chapter of one of the greatest feats of Soviet aviation ever conceived. The only clue is the building's size. It's gargantuan.

It needs to be. Because it contains something equally vast -- the largest airplane that was never completed.

The aircraft is an Antonov An-225, conceived by Soviet engineers in the dying days of the Cold War as a gigantic, gravity-defying workhorse that would help communism's ongoing race into space and assert the East's dominance of the skies.