Rapperswil-Jona is a municipality in the Wahlkreis (constituency) of See-Gaster in the canton of St. Gallen in Switzerland. It is located on the east shore of Lake Zurich. It is sometimes referred to as Rappi. In 2003 the municipalities of Rapperswil and Jona merged to form a new political entity. Rapperswil-Jona has a population of 24,400 (17,100 from Jona and 7300 from Rapperswil). This makes it the second largest town in the canton after the capital St. Gallen itself. The old city is dominated by the castle. The town is considered one of the most significant traffic junctions in the region. The Seedamm, a dam across Lake Zurich, links Rapperswil with Pfäffikon on the other side of the lake. This connection has been part of old pilgrimage routes.