The Roman Forum was built during the reign of Julius Caesar and his successor Augustus as an extension of the older Agora. As today, its main entrance was on the west side, through the Gate of Athena Archegetis. This gate marked the end of a street leading up from the Greek Agora, and its four surviving columns give a vivid impression of the grandeur of the original portal. On the side facing the Acropolis you can still make out an engraved edict announcing the rules and taxes on the sale of oil. At the opposite end of the Forum, a second gateway is also easily made out, and between the two is the marketplace itself, surrounded by colonnades and shops, some of which have been excavated. Inside the fenced site, but just outside the market area to the east, are the foundations of public latrines dating from the first century AD.
The best preserved and easily the most intriguing of the ruins inside the Forum site is the graceful octagonal structure known as the Tower of the Winds. This predates the Forum, and stands just outside the main market area. Designed in the first century BC by Andronikos of Kyrrhos, a Syrian astronomer, it served as a compass, sundial, weather vane and water clock – the latter powered by a stream from one of the Acropolis springs. Each face of the tower is adorned with a relief of a figure floating through the air, personifying the eight winds. Beneath each of these, it is still possible to make out the markings of eight sundials. On top of the building was a bronze weather vane in the form of the sea god Triton. In Ottoman times, dervishes used the tower as a tekke or ceremonial hall, terrifying their superstitious Orthodox neighbours with their chanting, music and whirling meditation.