Ephesus, the Roman capital of Asia Minor, had a mind-boggling population of half a million in the year 100. As a cultural and commercial hotbed, it attracted many of the important early Christians. Paul of Tarsus spent 5 years preaching in Ephesus. John the Apostle probably wrote his gospel and four other biblical books here. And Ephesus was where the Virgin Mary spent her retirement days.
As befitting a city of this stature (and four huge aqueducts), Ephesus had the largest outdoor theatre in the ancient world. It easily accommodated 44,000, usually for culturally redeeming events, but later in its history for sordid gladiatorial battles.
Eventually, the bay it was situated on silted up, stranding Ephesus inland. It was sacked by the Goths, then the Arabs, then forgotten for centuries. Now it’s packed with tourists. Unless you visit at the end of the day when, like a certain person in the stands, you can have this ancient city all to yourself.