girls, and St. Martin Busskirch is the former parish church of Rapperswil. Bollingen is known for the "Tower" built there by Carl Jung. Kempraten is one of the most important archeological sites in the canton of St. Gallen and is located at the norther shore of Obersee, the eastern part of Lake Zürich. History Settlements in the area of Rapperswil-Jona date back at least 5000 years. Evidence includes archaeological relicts collected from the Neolithic Seegubel site or the body burials of the La Tène culture. Centum Prata, after which Kempraten is named, is an important archeological site of the Gallo-Roman era. Atop the Lindenhof hill overlooking a former small village (Endingen), Rapperswil Castle was built around 1220 by the Counts of Rapperswil and is first mentioned in 1229. The town was founded when the nobility of Rapperswil moved from Altendorf across the lake to Rapperswil. The town was soon acquired by the Habsburg family who, in 1358/60, built the wooden bridge across the upper Lake Zürich. Later, the town bought itself free, and ending Old Zürich War made an alliance with the Swiss Confederation. Because of its strategic location along important infrastructure the town grew rich because of flourishing trade. This allowed a certain degree of freedom which was ended with the formation of Swiss cantons by Napoleon. Rapperswil was at first part of the Helvetic canton of Linth. After 1803's Act of Mediation, it joined the canton of St. Gallen. The locational advantage of the place attracted the national Circus Knie who built its headquarters in Rapperswil in 1919. The circus is now also responsible for the Knie's Kinderzoo and the Circus Museum. Cultural heritage After the Seedamm causeway and bridge were built in 1878, the Heilig Hüsli chapel was the only remaining structure of the medieval wooden bridge. It stood isolated in the lake and was not accessible to visitors until the reconstruction of the former wooden bridge was erected in 2001. The reconstructed wooden bridge is listed as Swiss heritage sites of national significance as part of the Seedamm area including Heilig Hüsli and the remains of the prehistoric wooden bridges respectively stilt house settlements. Located on Obersee lakeshore at the Seedamm isthmus, an ice age moraine (Linth Glacier) between the Obersee and the main body of the Zürichsee, the area was in close vicinity to the prehistoric lake crossings, neighbored by four Prehistoric pile dwelling settlements: