landhuis (or just huis), a ridderhofstad (Utrecht), a stins or state (Friesland), or a havezate (Drente, Overijssel and Gelderland). Some of these buildings were fortified. A number of castles associated with the nobility are found in the country. In Dutch, a building like this was called a kasteel, a slot, a burcht or (in Groningen) a borg. During the Dutch Golden Age in the 17th century, merchants and regents looking for ways to spend their wealth bought country estates and built grand new homes, often just for summer use. Some purchased existing manor houses and castles from the nobility. Some country houses were built on top of the ruins of earlier castles that had been destroyed during the Dutch Revolt. The owners, aspiring to noble status, adopted the name of the earlier castle. 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. Today there is a tendency to group these grand buildings together in the category of "castles". There are many castles and buitenplaatsen in all twelve provinces. A larger-than-average home is today called a villa or a herenhuis, but despite the grand name this is not the same as a manor house. Poland The architectural form of the Polish manor house () evolved around the late Polish Renaissance period and continued until the Second World War, which, together with the communist takeover of Poland, spelled the end of the nobility in Poland. A 1944 decree nationalized most mansions as property of the nobles, but few were adapted to other purposes. Many slowly fell into ruin over the next few decades. Poland inherited many German-style manor houses (Gutshäuser) after parts of eastern Germany were taken over by Poland after World War II. Portugal In Portugal, it was quite common during the 17th to early 20th centuries for the