The Cedar Ridge Observatory itself is very poorly detailed. It only consists of a semisphere on top of a cylinder, with a 'telescope' (modelled as a triangular shape), with a grey concrete texture. The observatory is normally inaccessible to the player. The ground it is situated on is not solid either, so the observatory is totally off-limits even if the player manages to reach it. This may explain the building's low level of detail. However, modifications exist for those who want to access the observatory point for any reason.
The observatory is featured on Rockstar's site for GTA III.