Ostrogski Palace, or Ostrogski Castle (Polish: Pa ac Ostrogskich, or Zamek Ostrogskich), is a mansion in the city center of Warsaw, on ulica Tamka. Begun by the powerful Ostrogski family who gave their name to the building, it currently houses the Fryderyk Chopin Society and Fryderyk Chopin Museum. The spot for the palace, a large lot of land on the Vistula escarpment directly below the Nowy wiat, was bought by Prince Janusz Ostrogski in early 17th century. As the area had been still a suburb of Warsaw and exempted from the laws of the city which prevented the inhabitants from building private fortifications, Ostrogski decided to build a small castle there.