In about 1150, the Benedictine Priory at Birkenhead was established. The monks used to charge a small fare to row passengers across the river. At this time, the Mersey was considerably wider with sand dunes and marshes to the north leading up to Ainsdale beach and sandstone cliffs and shorelines to the south near Otterspool. The only suitable landing point for the ferry was in the Pool, near the site of the present Merseyside Police headquarters. Weather often stopped crossings and passengers were delayed for days, taking shelter at the priory.