Colosseum. A.D. 72-80

The Colosseum is the first art historical place that I came across in my book, A Basic History of Art. It was an immense amphitheater for gladiator games in Rome. It is probably the most known of all of Rome's buildings. When it was built, it was one of the largest buildings; more than 50,000 viewers could be in the building at a time. It was designed so that people could easily move in and out of the structure.
I have seen numerous images of the Colosseum. I mostly saw it for it's size and scale. Janson points out the use of the columns. A column typically is comprised of a capital (top most section:think of it like a hat), a shaft and a base. Each level of the Colosseum had columns with different capitals. On the ground floor, Doric (simple and typically a basic square), the second floor, Ionic (two curved objects similar to a scroll) and the top two floors were Corinthian (highly decorative and similar to plants growing).
Today, the Colosseum is littered with tourists, contemporary greek soldiers trying to gather money from photos, vendors selling mini Roman sculptures and new technologies like group tours with headphones with monitors where you can hear your guide without being right next to him/her and the lazy man's ride, the Segway tour.
Basically, I am interested in how these places will remain the same. We learn about these places in our art history books, but how will these places be able to maintain themselves? Is it through tourists? Sightseers fork over quite a lot of money to view them up close. This means that the tourist is now part of the history of the place.