The architectural monuments of great importance are protected by the National Heritage Board of Poland. Over 100 of the country's most significant tangible wonders were enlisted onto the Historic Monuments Register, with further 17 being recognized by UNESCO as World Heritage Sites. Poland is renowned for its brick Gothic castles, granaries and churches as well as diversely-styled tenements, market squares and town halls. The majority of Polish cities founded on Magdeburg Law in the Middle Ages evolved around central marketplaces, a distinguishable urban characteristic which can be observed to this day. Medieval and Renaissance cloth halls were once an abundant feature of many towns.