The gymnasium was built on two levels. The upper terrace included the xystos, a covered portico 7 m wide and 178.35 m long, equal in length to a Pythian stadium. Here, athletes practised running during bad weather, and it was called xystos because its surface had to be scraped in order to be levelled. Recent excavations have revealed the xystos along its entire length. Originally, in the 4th century BC, it was built in the Doric order from porous stone; later, however, the Romans replaced the colonnade of the façade with an Ionic one, made of marble. Parallel to the xystos was the paradromis, a levelled open-air track 6 m wide, used for training in running events. On the lower terrace was the palaestra, which included a square central courtyard surrounded by porticoes, divided into rooms. Inscriptions inform us about the use of these rooms as a ball-playing area (sphaeristerion), a changing room, a room for dusting the body (konima), and possibly also a sanctuary of Hermes or Heracles. In the courtyard, athletes practised wrestling and boxing. To the west of the palaestra, a circular pool is still preserved, with a diameter of 10 m and a depth of 1.80 m, constituting an essential element of the Greek bath. Behind it, a series of water spouts supplied water from the Castalian Spring to ten stone basins, which communicated with one another. These were the athletes’ washing basins. Further west, in 120 AD, a balaneion or Roman baths were built for hot bathing. A few centuries later, the area of the gymnasium was occupied by a Byzantine monastery. Its katholikon, which had been built above the palaestra, was demolished in 1898 in order to carry out the excavations. In fact, on one of the Classical columns, which had been reused in the monastery, Lord Byron carved his name when he visited Delphi.