Side Ancient Theater

The Side Theater was built in the 2nd century AD. It could seat approximately 15,000 people. Initially, it was probably only used for plays, but later it was used for animal fights. What's special about this theater is that, unlike other theaters, the seating is not built into a surrounding slope, but rather is suspended freely on high vaulted ceilings.

The formerly classical Greek theater was expanded by the Romans with additional tiers of spectators (cavea) in a 180° arc, slightly larger than a semicircle, and provided with a circular stage (orchestra) for performances.
The site had already been chosen by the Greeks to take advantage of the natural gradient of a local hillside, which was often rewarded with a wonderful view of the landscape.
During the heyday of Greek tragedies and comedies (5th century BC), a raised stage (scenae) was initially built, initially made of wood, which was later replaced by stone in the Hellenistic era.
The Romans preferred to completely enclose the theater with an additional inner wall, which was also built behind the stage, but which retained the Greek form of the tiers. The side entrances (parodos) were never roofed in the Greek era; the Romans combined the entire structure into a large building complex with covered entrances. If there were no natural slopes for the cavea, they were built on an artificial elevation, e.g., in the form of archways. The rows of benches were usually separated by a horizontal corridor (diazoma).
Source:
alaturka.info/de/tuerkei/tuerkische-riviera/side-manavgat/355-theater-von-side

The (Roman) theater of Side was restored to its current state in the middle of the 2nd century AD. About a century later, the orchestra was converted for arena combat. The theater was built on the transition to the headland. Due to the lack of a hill, a double-arched gallery with a surrounding corridor was constructed. Twenty-three vaulted passageways lead to the ambulatory (diazoma) between the first and second tiers.
It is assumed that a surrounding arched gallery was built above the uppermost rows of seats—parts of which have been preserved in the theater of Perge, for example—to enhance the acoustics. Unfortunately, no remains of this gallery have survived. It was probably destroyed over time by earthquakes, the stones fell, and were used to build the Byzantine defenses.
The two-story stage house was 65 meters long and 10 meters wide. The two floors were 20 meters high. Five doors lead to the neighboring commercial agora. Some sources report the theater's temporary use as a slave market.
Source:
reiseinfo-tuerkei.de/Tuerkei/Theater/Side.htm