Uncover the technological leaps forward that allowed the world's largest spanning dome - the Oita Stadium in Japan - to be built. The Oita's colossal roof spans a mighty 274 metres. A steel, Teflon and titanium structure over 270 metres across and 60 metres high, the Oita Stadium roof covers a sports stadium big enough to seat 43 thousand spectators. At the flick of a switch its seats retract to reveal a running track and its roof opens and closes like a giant eye. Count down the technological leaps in six landmark domes including Rome's Pantheon and Florence's Cathedral, that allowed this, the world's largest spanning dome, to be built.