It was where sand or dust was stored, for use by wrestlers after they had been anointed with oil.
[1] The purpose of this was so that during a fight, the oil or sweat would not prevent a wrestler from having a good grip on his opponent.
[3] After a fight, or exercise, the powder was rubbed off with strigils, before the wrestler had a bath.
[4] The conisterium was built after the coryceum and next to a cold bath[5] called frigida lavatio.
[1] In the palaestra of Vitruvius, for instance, the gymnasium chambers were built on the right side while the elaeothesium, tepidarium, and an unidentified chamber on the left.