Inaugurated in 80 AD, the Flavian amphitheatre or Colosseum is the biggest in the Roman world (the axes of this rounded oval measure 188m and 156m). Three levels of arcades enclose this impressive arena, a masterpiece of Ancient Roman architecture, which was once able to seat 50 000 spectators who came here to watch circus games, gladiator fights and even naval battles. Ambitious restoration work has returned the building to its former glory.