M.C.L.A.D.
The Monolithic Door is best described by its official name: the Monolithic Contoured Laterally Moveable Access Door. Constructed as a one-piece, three-dimensional, curved panel, the Monolithic Door can move laterally on the inside or the outside of a Monolithic Dome.
Image from The MCLAD: Monolithic Contoured Laterally Moveable Access Door story