The Kleiner See is bounded in the east by the 150-metre-long Landtor Bridge (Landtorbrücke), over which the Chelles Allee runs, and in the west by the 410-metre-long railway causeway and covers an area of around 20 hectares.

The smaller formerly separate island of Hintere Insel is located west of the historical town wall and the old moat.

This rear part of the island was enlarged around 1970 by a good four hectares, by the reclamation of an area of the lake between the Pulverschanze and the Sternschanze.

It now covers an area of eleven hectares, about one sixth of the island and is dominated by the Lake Constance Clinic of ENT physician and cosmetic surgeon, Werner Mang.

The westernmost point of the Hintere Insel and of the whole island is marked by the 1508 Powder Tower and the former Luitpold-Kaserne built in 1902/03.