Complex sentence: It was first mentioned in the 1280s at its first location at the present Zürichhorn, and supported by the House of Rapperswil, namely by Elisabeth von Rapperswil and their children by second marriage.
Split into simpler sentences: It was first mentioned in the 1280s at its first location at the present Zürichhorn. The founding was supported by the House of Rapperswil, namely by Elisabeth von Rapperswil and their children by second marriage.