Vestibule refers to the antechamber of the private quarters of emperor Diocletian. It is the only section of the emperor’s private apartments that has been preserved in elevation. Typically, officials visiting the emperor would first pass through the Golden Gates of the palace, then take the long walkway (present-day Diocletian’s Street) towards the Peristyle, where they would pass through the protyron and enter the vestibule only to continue down another large corridor from where they would be taken to the reception hall or, perhaps, the triclinium.
Rectangular on the outside, vestibule is rounded from the inside. It was originally a domed structure with a mosaic ceiling and marbled walls, whose four niches, still visible today, housed long lost statues.
Today, most visitors marvel at the ‘eye’ in the place of the lost dome above it, which provides a sight for many a picture. During the summer months, vestibule often draws local klape, the a cappella groups that perform the traditional Dalmatian folk songs.