This 12th-century cathedral is topped with a 16th-century Renaissance dome. Its interior boasts a number of tombstones and altarpieces, and polychromatic art nouveau frescoes. The royal chapel holds the sarcophagi of two Polish kings, Władysław Herman and his son Bolesław Krzywousty, who lived in Płock during their reigns. Both are in immaculate condition (the tombs, not the kings).
Take time to note the bronze doors at the southern end of the cathedral – copies of the original 12th-century doors commissioned by the local bishops. The originals disappeared in mysterious circumstances and reappeared in Novgorod, Russia, where they remain today.