Colosseum in Rome
Most people have heard of the Colosseum in Rome, but there were many other amphitheaters all over the Roman Empire. The first gladiatorial fights, in Etruscan times, were held anywhere that there was a flat place near a hill, so that people could sit on the hillside and watch the fights being held down on the flat area. But there isn't always a convenient hill like that, so before long, around 300 BC, rich men and city governments started to build temporary wooden amphitheaters for people to sit in, like artificial hills, or like the seating for events at county fairs or festivals today. They were called amphitheaters because they were built like two theaters facing each other.
The amphitheater in Pompeii
By the last years of the Roman Republic, though, there were so many gladiatorial fights that people got tired of putting up these wooden amphitheaters and taking them down again. Big towns began to build permanent amphitheaters out of limestone and marble. The first stone amphitheaters were not built in Rome, but in Pompeii and other smaller towns in Italy.
The Colosseum in Rome
In the time of the Roman Empire, nearly every town of more than a few thousand people had its own stone amphitheater, all over the Roman Empire from Syria to Spain, and from England to Tunisia. Many of these are still standing (at least part of them is still standing) even today, and you can go visit them.
To find out more about Roman amphitheaters, check out these books from Amazon.com or from your library:
Make This Model Roman Amphitheatre, by Iain Ashman (1995).
Roman Architecture, by Frank Sear (1983). The standard college textbook.
The Roman Amphitheatre: From its Origins to the Colosseum, by Katherine Welch (2004). By a specialist, for specialists.