The Hoo Peninsula is a peninsula in Kent, England, separating the estuaries of the rivers Thames and Medway. It is dominated by a line of chalk, clay and sand hills, surrounded by an extensive area of marshland composed of alluvial silt. The name Hoo is a Saxon word believed to mean 'spur of land' or refers to the 'distinct heel-shape of the ridge of hills' through Hoo. Hoo features in the Domesday Book. The peninsula is home to internationally and nationally protected wildlife sites as well as industrial facilities and energy industries. History The Romans have been credited with the first two attempts at building a sea wall. The subsequent draining of the marshes created pastureland to support sheep. The area is rich in archaeology. Bronze Age implements and Jutish cemeteries have been found on the peninsula, and Roman pottery at Cooling. It was once the point of departure across the ancient Saxon fording point over the River Thames to Essex. Much of the peninsula lies in one of the Saxon divisions of England called "hundreds": here it is the "Hundred of Hoo". To be precise, the Hundred comprised the parishes and churches of Hoo, High Halstow, St Mary Hoo, Allhallows and part of Stoke. The Isle of Grain, then a complete island, was in the Hundred of Gillingham; the remainder of the parish of Stoke was in the Hundred of Shamel. William the Conqueror granted his half-brother, Odo, the large estate of Hoo. During the First World War this peninsula was the site of an explosives factory and storage facility. Geography The marshes The Peninsula's marshlands are part of the North Kent Marshes and now form a major part of two protected areas: the Thames Estuary and Marshlands, and the Medway Estuary and Marshes. The Thames Estuary area covers the 15 miles (24 km) from Gravesend to the Isle of Grain; the Medway Area 15 miles (24 km) from Rochester to the Isle of Grain: a total of 38 square miles (98 km2) of marshlands. Both are Sites of Special Scientific Interest (SSSI) and Special Protected Areas (SPA). They include coastal grazing marsh, intertidal mudflats, saltmarsh and lagoons. On the line of hills lies the Northward Hill National Nature Reserve. Nature reserve The Hoo Peninsula is home to a 129.7 acre nature reserve located in High Halstow, one of the many villages on the peninsula, called High Halstow NNR.