Throughout the 19th century, the estuary was home numerous cement works and brickfields, producing much what helped build the rapidly expanding London suburbs. People have lived and worked around the estuary for thousands of years and as a result it is rich in both archaeological and historical remains including Rochester and Upnor castles and Chatham Dockyard. To the east, Faversham was a major producer of gunpowder from the 16th century, but today the estuary is of international significance, both environmentally and economically not least because it is a major trading route. Despite the industrial landscape, the estuary continues to support an impressive and diverse ecosystem, providing the perfect habitat for thousands of protected birds. In 2013 the Medway Estuary was designated a Marine Conservation Zone, protecting one species (the tentacled lagoon-worm) and eight different habitats.