It soon became one of the largest and most active monasteries of Germany from which a number of other foundations were made: Schönau Abbey near Heidelberg in 1142; Otterberg Abbey in the Palatinate in 1144; Gottesthal Abbey near Liege in 1155; and Arnsburg Abbey in the Wetterau in 1174. At its height in the 12th and 13th centuries, the population is estimated to have been about 100 monks and over 200 lay brothers. The 18th century however was a period of great economic success: surviving accounts show that the abbey profits were regularly invested on the Frankfurt money market.