A treatment plant for treating workpieces having a treatment installation having a housing which defines a treatment space and a conveyor system having a multiplicity of transport trucks for conveying workpieces through the treatment space. Each transport truck has a running gear and a fastening installation for at least one workpiece, the running gear and the fastening installation being coupled to one another by a connection installation. A running space for the running gear is present outside the treatment space, the running space connected to the treatment space by a connection passage in the upward direction so that the running gear is capable of being moved in the running space, wherein the fastening installation is conjointly carried in the treatment space and the connection installation extends through the connection passage. A cover installation having at least one walk-on cover element is present in the treatment space, the cover element being capable of being moved between a walk-on position in which the cover element covers the connection passage and a release position in which the cover element can be passed by the connection installation of one of the transport trucks.