VESTIBUL is the first part of the imperial corridor that led from Peristil through the protir to Dioclecian`s residential part of the Palace. The main characteristic is its circular interior and a big opening through which the bell tower of Saint Domnius can be seen. The opening used to have a dome which was in white stone decorated with a glittering coloured mosaic and semicircular niches filled with statues. Today, during summer time it is used as a popular place for singing traditional Croatian accapela music (klapa).