Ostrvica
... that Ostrvica was the main castle in the region of Rudnik in Serbia at the end of the Middle Ages?
... that <b id="mwCW4"><a class="mw-redirect" href="./Ostrvica_(castle)" id="mwCW8" rel="mw:WikiLink" title="Ostrvica (castle)">Ostrvica</a></b> was the main castle in the region of <a href="./Rudnik_(mountain)" id="mwCXA" rel="mw:WikiLink" title="Rudnik (mountain)">Rudnik</a> in Serbia at the end of the <a href="./Middle_Ages" id="mwCXE" rel="mw:WikiLink" title="Middle Ages">Middle Ages</a>?