After entering the slave era, what factors in the Roman Empire promoted the formation of the tourism phenomenon?

The first is the material basis. The wealth of Rome was unique and certainly second to none. Relying on long-term conquests, citizens accumulated a large amount of wealth. The second is the improvement of Roman people's cultural taste. Some guilds, including slaves, sought sponsorship from wealthy people to hold activities such as unit group tours today. The third is developed transportation. The close relationship between tourism and transportation needs no explanation. Rome's transportation is known as "all roads lead to Rome". The rules in Rome are that you can drive at night and only walk during the day, but for long trips out of Rome, you can take a stagecoach or horseback. From the perspective of the safety of cross-sea travel, the six-month dangerous voyage from the Gulf of Aden in Arabia to India has been opened, and it is not difficult for cruise ships to reach the coasts of the United Kingdom, France, Russia, and Northern Europe.