Many visitors to Frodsham won't notice this rock at the end of Main Street (at the junction of Marsh lane) and even residents will wonder what it is supposed to be. The "Brook Stone" is a glacial erratic. A glacial erratic is glacially-deposited rock differing from the size and type of rock native to the area in which it rests - carried by glacial ice. Once such example can still be seen today at the junction of Marsh Lane and Main Street. It has not quite reached the level of prominence as the Holy stone of Clonrichert (a 'Father Ted' reference) but nevertheless its the oldest rock in Frodsham.