A door comprising: a door leaf movable along a path defined by a guide rail arrangement between a closed position, in which it is arranged approximately in a vertical plane, and an open position, in which it is arranged overhead in approximately a horizontal plane, said door leaf having a plurality of door leaf members arranged one behind the other in the direction of movement of the door leaf and connected to each other in a hinged manner in respect of hinge axes running perpendicular to the predefined path, wherein the guide rail arrangement has two guide rails arranged in the area of the lateral edges of the door leaf running parallel to the predefined path, each guide rail having a first section which runs substantially rectilinearly, approximately parallel to a lateral edge of the door leaf in the closed position approximately in the direction of gravity, a second section which runs substantially rectilinearly approximately parallel to a lateral edge of the door leaf in the open position, and an arc-shaped section connecting the rectilinear sections, a drive device connected to the door leaf and including an electric motor, a transmission arrangement coupled to said electric motor and a motor control, and a counterweight device assisting the opening movement of the door leaf, characterised in that the polygon ratio of the radius of curvature of the arc-shaped section on an inner guiding surface of said section to the height of at least one door member in a direction perpendicular to the hinge axes and approximately parallel to the predefined path is 0.6 or more and 0.8 or less and the electric motor has a frequency-controlled motor. a door leaf movable along a path defined by a guide rail arrangement between a closed position, in which it is arranged approximately in a vertical plane, and an open position, in which it is arranged overhead in approximately a horizontal plane, said door leaf having a plurality of door leaf members arranged one behind the other in the direction of movement of the door leaf and connected to each other in a hinged manner in respect of hinge axes running perpendicular to the predefined path, wherein the guide rail arrangement has two guide rails arranged in the area of the lateral edges of the door leaf running parallel to the predefined path, each guide rail having a first section which runs substantially rectilinearly, approximately parallel to a lateral edge of the door leaf in the closed position approximately in the direction of gravity, a second section which runs substantially rectilinearly approximately parallel to a lateral edge of the door leaf in the open position, and an arc-shaped section connecting the rectilinear sections, a drive device connected to the door leaf and including an electric motor, a transmission arrangement coupled to said electric motor and a motor control, and a counterweight device assisting the opening movement of the door leaf, characterised in that the polygon ratio of the radius of curvature of the arc-shaped section on an inner guiding surface of said section to the height of at least one door member in a direction perpendicular to the hinge axes and approximately parallel to the predefined path is 0.6 or more and 0.8 or less and the electric motor has a frequency-controlled motor.