1. A rotary observation tower comprising a vertically extending frame, chain wheels rotatably mounted on the upper part and the lower part of the said frame, a pair of endless chains wound around said chain wheels, driving means coupled to at least one of said chain wheels for driving said one chain wheel, outwardly protruding arms mounted on the said pair of endless chains at spaced intervals, horizontal support means rotatably mounted on the external end of each arm centering and rotatably around a horizontal axis which is parallel with the axis of the chain wheels, a gondola having the upper end rotatably mounted on said support means for rotation around a perpendicular axis, a guide rail on said frame so curved as to constitute a part of a helix, and guide wheels on the outside of the gondola engageable with said guide rail during movement of said chains to cause the gondola to rotate around said perpendicular axis as it is moved along said guide rail on said chains.