The upper part of the Colosseum was originally made of wood, but was converted to stone after the year 223. Its outer framework and structure were composed of gigantic blocks of travertine, which is a type of limestone. The rest of the structure was composed of softer, lighter stone, and was usually faced with marble. The Colosseum rises 150 ft, and is divided into four stories. The interior of the Colosseum consisted of the arena, which was a wooden floor that sustained a bed of sand. It covered an area of about 76m by 46m. The Colosseum could accommodate about 70,000 people who came to watch the gladiatorial combats and wild beast hunts.