Colesseo - the more things change, the more they don't. This is the venue for the original blood sport (now UFC). It had the capacity to hold 20% of their population. It is multiple leveled plus the subterranean area where it is compartmentalized ( for the gladiators and exotic animals). The coliseum has been looted of many materials before, so it is not in fantastic and complete state. (better condition but smaller is the one in Arles in France)
Forum - is an early Roman village/community. It is made up of housing, commerce space, gymnasium and other necessities of a civilization.
Arch of Constantine - the model for the one in Paris.
The bathhouse - wow, those Romans knew how to pamper themselves. Magnificent and enormous skeleton of the structure.