Systems and related methods related to structures with large-scale rotatable elements. Some of the present systems comprise: a tower; a tower hub coupled to the tower and having a transverse dimension of at least 50 feet; an observation wheel rotatably coupled to the tower and having a central wheel hub; a plurality of roller bearings disposed between the tower hub and the wheel hub to rotatably support the observation wheel relative to the structure, the roller bearings each having a diameter that is less than one quarter of the transverse dimension of the wheel hub.