The name “Colosseum” originated from Italian word “colosso” that means “colossal”, “enormous”. The length of Coliseum is 188 m., width 156 m., height 57 m. Lower rows in Coliseum belonged to the Emperor, senators, judges, and other noble men. Some seats of the most important persons had been named after them. Seats in upper rows were taken mostly by women. Last rows were usually intended for slaves that operated 36 elevators.
This amphitheatre was built about 2000 years ago. Roman citizens enjoyed games in this "circus" , how it was called. The amphitheatre could host 50,000 spectators for one show.

Sources, related links:
Wikipedia - Colosseum
The COLOSSEUM — a site on the Roman amphitheatre