St. Petersinsel or Île de St-Pierre (English: St. Peter’s Island) is a peninsula situated in Lake Biel in the canton of Bern, Switzerland. It was formed in the last Ice Age (see Pleistocene), when the Rhône Glacier reached as far as the Jura mountains. It is a promontory of the Jolimont, above Erlach.
In the late nineteenth century following the engineering works of the Jura water correction, the water-level of the three lakes of the Seeland have dropped enough to clear the until then hidden isthmus, linking Erlach to St. Petersinsel, which has eversince become a peninsula.
Monks of the Cluniac order were the first inhabitants of the island, and built a monastery here in 1127.
Before his expulsion, Jean-Jacques Rousseau, spent two months on the island in 1765 calling it the "happiest time of his life".[1]