Door's track
Instead of inside, the track from which the Monolithic Door hangs can be installed on the dome’s outside. “That’s another advantage,” David pointed out. "That makes it possible to construct a huge Monolithic Dome or Crenosphere as a stadium, for example, and equipping it with a Monolithic Door that, when opened, turns the facility into a huge amphitheater.
Image from The MCLAD: Monolithic Contoured Laterally Moveable Access Door story