The ground plan of the palace is an irregular rectangle measuring east: 214.97 m, north: 174.74 m, south: 181.65 m (adjusting for the terrain), with sixteen towers projecting from the western, northern, and eastern facades on the facades facing the mainland. There are four towers on the corners of the square, giving the palace a characteristic of the
legionary forts similar to those on the
Danube. Two of the six octagonal ground-floor towers were framed by three landing entrances, the six rectangular ground floors of the rectangular floor being between the corner and the octagonal. To date, three corner towers (except the southwestern) have been preserved, and only the remains of octagonal and rectangular ones. Three well-preserved landings have been architecturally fragmented, especially the northern one, which was the main approach from
Salona. The south,
seaside gate, is small, simple and well-preserved. The facade walls of the palace in their lower parts are massive and simple without openings, and in the upper part, there are large arches that face the land, i.e. on the west, north and east facades.
Subterranean portions of the palace feature
barrel vaulted stonework. Anne Hunnell Chen proposes that
Sasanian palace design may have been a significant influence on Diocletian's Palace, particularly given that Diocletian and his co-rulers had personally campaigned on Persian soil before the palaces were constructed. Chen observes that the spatial arrangement of the palace, while mirroring Roman military camp layouts, also closely aligns with the characteristic spatial organization of early Sasanian royal palaces. The pitched brick dome construction technique was unprecedented in Roman imperial architecture prior to the late 3rd century and had roots in
Mesopotamian building tradition. Chen suggests it may have reached the Roman world through architects and engineers who accompanied troops on the Persian campaigns. She concludes that the adoption of Persian architectural elements resulted from Rome's decisive victories over the Sasanians in the late 3rd century. In their aftermath, the imperial administration opted to incorporate recognizable markers of Eastern palaces to project power in a visual language legible to both domestic and international audiences. Today the 7th-century church of
St Martin can be found above the gate, and is open to the public.
The East Gate The Porta Orientalis ("the eastern gate") is one of the four principal Roman gates into the Palace. Originally a secondary gate, it faces east towards the Roman town of Epetia, today
Stobreč. Probably in or around the 6th century, above the gate in the sentry corridor, a small church dedicated to St Apolinar was built. This coincided with the complex seeing an
influx of refugees from outlying communities, similar churches were over the
Golden Gate, the
Iron Gate, and the
Bronze Gate. The structure of this part of the wall and the door itself were later incorporated in various buildings in the following centuries, such as the Church of Dušica, which was destroyed in the Second World War. is one of the four principal Roman gates into the Palace. Originally a military gate from which troops entered the complex, the gate is the only one to have remained in continuous use to the present day. During the
persecutions under Theodosius I a relief sculpture of
Nike, the Roman goddess of Victory (which stood on the lintel) was removed from the gate, later in the 5th century,
Christians engraved a
Cross in its place. In the 6th century, above the gate a small church dedicated to
St. Teodora. This coincided with the complex seeing an
influx of refugees from outlying communities, similar churches were over the
Golden Gate, the
Silver Gate, and the
Bronze Gate.
The South Gate The Porta Meridionalis or "the southern gate" is the smaller of the four principal Roman gates into the Palace. Originally a sea gate from which the Emperor entered the complex by boat, via basement rooms in the Imperial Palace.
Inner layout The design is derived from both
villa and
castrum types and this duality is also evident in the arrangement of the interior. The transverse road (
decumanus) linking the
Eastern gate and
Western gate divided the complex into two halves.
Southern half In the southern half there were more luxurious structures than in the northern section; these included public, private and religious buildings, as well as the
Emperor's apartments.
Emperor's apartment The
Emperor's apartments formed a block along the seafront, with an exterior square and circular floor plan, with a dome. From there, one approached the Emperor's apartment, which stretched 40 m deep along the entire south facade; it is only partly preserved on the upper floor, but its ground-floor, translated substructures that directly bore it are almost completely preserved, so the overall layout and appearance of the upper spaces can be seen given the coincidence of the upper and lower floor plans. On the west side of the upper floor are preserved the remains of a dome hall and two halls with apses, and on the east side are parts of an octagonal dining room (
triclinium) with three halls with a cross floor plan. The wall of the Western Cross Hall is preserved at full height. Diocletian's apartment was interconnected by a long room along the southern façade (cryptoporticus) from which through 42 windows and 3 balconies a view of the sea was opened. Two baths were recently found north of the Emperor's apartment, one adjacent to the west and the other to the eastern halls. Although for many centuries almost completely filled with refuse, most of the substructure is well preserved and indicates the original shape and disposition of the rooms above.
The Vestibule A rotunda, that was once the first section of the imperial corridor in the Palace that led via the Peristyle to the Imperial apartments of the Palace.
The Palace Cellars Set below what were the Imperial apartments, the
Cellars of Diocletian's Palace are a set of substructures located at the southern end of the Palace, that represent one of the best preserved ancient complexes of their kind in the world.
Peristyle at the Peristyle A monumental court, the Peristyle, formed the northern access to the imperial apartments in front of the Vestibule. It also gave access to Diocletian's mausoleum on the east (today the
Cathedral of Saint Domnius) and to three temples on the west (two of which are now lost, with the third, originally being the
temple of Jupiter, becoming a baptistery). There is also a temple just to the west of the Peristyle called The Temple of
Aesculapius, which has a semi-cylindrical roof built of stone blocks, which did not leak until the 1940s when it was covered with a lead roof. The temple was recently restored.
Egyptian sphinxes The Palace was decorated with numerous 3500-year-old granite
sphinxes, originating from the site of Egyptian Pharaoh
Thutmose III. Originally twelve
sphinxes brought from Egypt by Emperor
Diocletian. Scottish architect
Robert Adam considered this temple to be one of Europe's most beautiful monuments. Only three have survived the centuries. One is still on the Peristyle, the second sits headless in front of
Jupiter's temple, and a third is housed in the city museum.
Temple of Jupiter Dedicated to the Ancient Roman god
Jupiter, it is located in the western part of the southern section of the Palace complex, near the
Peristyle. It was built between 295 and 305, during the construction of the Palace. Since the Emperor unexpectedly abdicated the throne in 305 and arrived at the palace from
Nicomedia earlier, finishing work on the construction of the Palace was stopped so parts of the Temple remained unfinished. The temple was later converted into a church, probably a Baptistery of St.
John the Baptist in the 6th century, at the same time when the crypt dedicated to
St. Thomas was built.
Northern half The northern half of the palace, divided into two parts by the main north–south street (
cardo) leading from the
Golden Gate (
Porta aurea) to the Peristyle, is less well preserved. It is usually supposed that each part was a residential complex housing soldiers, servants, and possibly some other facilities.
Streets and annex buildings Both parts of the palace were apparently surrounded by streets, leading to the perimeter walls through a rectangular buildings (possibly storage magazines). ==Filming location==