Simplify the following text for a Grade 6 native English-speaking person.
Original: The borough borders the City of London and the London Borough of Tower Hamlets to the north ( the River Thames forming the boundary ) , the London Borough of Lambeth to the west and the London Borough of Lewisham to the east . To the south are the London Borough of Bromley and the London Borough of Croydon .
Simplified: The London Borough of Southwark is a London Borough .