Overview: How does a dome support itself? Ever since the Roman Emperor Hadrian topped his Pantheon with a dome, this roof-with-class has been the prestige building form. Big domes cover civilization's most revered structures, from great cathedrals to mosques to houses of government. Host David Macaulay uncovers the tricky technology of domes, from the Pantheon to the geodesic marvels of Buckminster Fuller and beyond.