The Colosseum or Coliseum, was actually called Flavian Amphitheatre (Latin: Amphitheatrum Flavium; Italian: Anfiteatro Flavio or Colosseo) (you can still see ‘Amphitheatrum Flavium’ used today). The Colosseum in Rome is always capitalized and is also spelled differently.
The Colosseum had about 80 entrances (76 for the general public and 4 special un-numbered gates which were the Grand Entrances). The East entrance/exit was the ‘Gate of Life’ (Porta Sanavivaria) where the gladiators entered the arena and the west entrance/exit was the ‘Gate of Death’ (Porta Libitinensis), exit that dead gladiators were carried out from.
This ruin is actually home for some 200 different species of flora. It’s said to have had 684 species of plants during it’s peak.
The maintenance costs (of acquring animals and gladiators) shot up the roof and hence the gladiator fights were stopped in 435 CE and eventually the animal hunts in 523 CE.
Why Colosseum? Colosseum was actually built near the giant statue of Colossus (part of the Nero’s Park). The name Colosseum has long been believed to be derived from it.