These country houses or stately homes (called "buitenplaats" or "buitenhuis" in Dutch) were located close to the city in picturesque areas with a clean water source. Wealthy families sent their children to the country in the summer because of the putrid canals and diseases in the city. A few still exist, especially along the river Vecht, the river Amstel, the Spaarne in Kennemerland, the river Vliet and in Wassenaar. Some are located near former lakes (now polders) like the Wijkermeer, Watergraafsmeer and the Beemster. In the 19th century, with improvements in water management, new regions came into fashion, such as the Utrecht Hill Ridge (Utrechtse Heuvelrug) and the area around Arnhem.