Colonnades are an important part of some Hellenistic and most later Roman architecture, unrivalled for their combination of shade and swank in the very best urban environments - compare present-day Bologna. At Split, they form the backbone of the internal city plan, and lead the visitor to the area in front of the (ex-)Imperial Apartments:
In fact, it was the colonnades which especially impressed early visitors, one of which even suggests that part of the great sea-facing portico was still open in the 17th century:
Even today, although much of the interior of the palace is clogged with (splendid) 17th century palaces and other late buildings, it is the colonnades which impress, as the plan itself demonstrates.
Here is what the colonnades would have looked like, according to Georg Niemann's reconstruction of 1910:
Such colonnades were a fixture in many Hellenistic and Roman cities, especially in the East - as here at Palmyra. The south-east face of the monumental arch, with the colonnades beyond, is seen here from Robert Wood's Palmyra of 1758:
Unfortunately, another type of colonnade at Split has vanished, its materials probably being re-used for house-construction, or later fortifications. This is the great aqueduct which ensured a plentiful water-supply, not just for essentials, but for the much more important luxuries, such as fountains and baths:
Use this model of the Palace, or go to the Entrance
Hall