Essex is today a county in southeast England, between London and the North Sea One of the "home counties", it borders Suffolk and Cambridgeshire to the north, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and London to the southwest. The county town is Chelmsford, the only city in the county and it has Roman ruins and the Norman-era Colchester Castle, with a museum. Southwest, 18th-century Hylands House in Chelmsford is set amid vast parklands. To the north is the medieval market town of Saffron Walden, home to Jacobean estate Audley End House and Gardens There are three definitions of the extent of Essex, the widest being the Ancient County, the more usual being the smaller Ceremonial County and smallest being the administrative county-the area administered by the County Council and which excludes the two unitary authorities of Thurrock and Southend-on-Sea The Ceremonial County occupies the eastern part of what was, during the Early Middle Ages, the Kingdom of Essex