Also known as the Scawen Grotto, after Thomas Scawen who created it in 1724. He had inherited Carshalton Park from his uncle. It is said that the grotto might be a case of one-upmanship, since the owners of Carshalton House, the Fellowes family, had built a grotto beside the lake.
The Scawen Grotto was constructed over springs which source the River Wandle. It was made to look like a sea cave with a marble sea shell basin, and decorated with a variety of materials including coral and shells and a statue of Neptune.
The water supply used to be plentiful – once 3.5 million gallons a day, flowing up the Westcroft Canal to power Grove Mill before continuing its journey in the River Wandle. However, over-pumping of water for public use in the Croydon area caused the water table to drop and the grotto and canal dried out.
After months of heavy rain in 2014, waters flowed from the grotto for a while, so locals could glimpse a landscape from the past.