Salgótarján is a city in northeastern Hungary, in the county of Nógrád. It is the administrative and economic centre of the Nógrád region. The city is located in the valley of the river Salgó, surrounded by the Bükk Mountains. The city was first mentioned in 1206 as a fortification of the Gutkeled clan. The town developed around the 14th century Gothic castle of the Salgói family. The city walls and many of the city's buildings were built in the 17th century. The city is home to the Salgótarján Castle, the Salgótarján Open-Air Museum, the Károlyi Castle, the Széchenyi Mansion, and the Rákóczi Mansion.