The Colosseum is an oval amphitheater built in the center of Rome between AD 72 and 80. It is built of Travertine limestone, volcanic rock, and concrete. It was the largest amphitheater of its time and held 50,000 to 80,000 spectators. In 2018, it was the most popular tourist attraction in the world, with 7.4 million visitors. I can understand why.
This is a place I've read about and seen on television programs and in movies and I was happy I was able to see it up close. I'm amazed it is still standing after so many years.