 Bristol is part of a limestone area running from the Mendip Hills in the south to the Cotswolds in the northeast. The rivers Avon and Frome cut through the limestone to the underlying clay, creating Bristol's characteristically hilly landscape. The Avon flows from Bath in the east, through flood plains and areas which were marshes before the city's growth. To the west the Avon cuts through the limestone to form the Avon Gorge, aided by glacial meltwater after the last ice age.
