In the Colosseum, 50,000 people could watch games, but it wasn't easy to build a place for so many people. The platform where they sat needed to be strong and not collapse. To make it strong, the designers used something called an arch.
An arch is a special structure that looks like a half-circle made of stones or bricks. It is very strong because it can distribute the weight sideways, which means it can hold up heavy things. The Romans used arches to build the walls and tunnels in the Colosseum.
The people in Rome used arches in many other structures too, like bridges and tunnels for water. Even though they were built a very long time ago, many of these arches are still standing today. They show us how smart the Romans were to invent this amazing technology.
