I only have a glancing knowledge of the kinds of hijinks that went on in this place. From what I can tell it was quite a barbaric scene, but if you don’t mind my saying so, not always without artistic value.
What stories do you know from the Coliseum? I am interested in the depraved, the political, but also the kind of thing one would perhaps not expect. If you have any good links or sources, post 'em.
Well, I saw Springsteen there for three shows back in 1985. You can hear me in the background of “The River” from his live album. I’m the guy yelling “Bruuuuuuuce!”
I meant the Roman Coliseum.
You have no idea how old silenus is.
And he was yelling “Brvvvvvvce”!
I love what smartasses you guys can be sometimes 
First, nitpick, it’s Colosseum (or, alternatively, the Flavian Amphitheatre).
It is said that there was once a time when they flooded the stage area and staged mock naval battles called Naumachiae. They were reproductions of naval battles from history where criminals or real sailors fought each other.
Here is a picture I took while visiting the underground almost two years ago of what is thought to be one of the boat docks. This is another place they thought was a dock, as well.
One time I went to the Colosseum with some friends, one night. I was tipsy from the wine we’d had. There was another group of people there, and it was the birthday of one of the group members. When those guys found out that my friends and I were musicians, they asked us to sing Happy Birthday for them. Good times.
(Not sure if that’s what the OP was looking for. 
)
Or Bruuuuuuuuutus!
–Golf Clap–
Been there. Had the planet’s WORST pizza in a small cafe built into a holding cell. ( Seriously. )
I love the idea that they had water battles. They were that good at engineering. Freakin’ brilliant. And savage.
Cave ne ante ullas catapultas ambules. 
“Thumbs up” = life?
“Thumbs down” = death?
That’s a 19th Century fabrication. We don’t actually know what signals they used. The Latin texts are unclear on the subject.
Many modern scholars believe that the death signal was the thumb turned toward the body or the neck, meaning “stab him”.
The mercy signal may have been thumb down, meaning “drop your sword”, or thumb clasped within the fist, meaning “sheathe your sword”.
The death blow was probably given where the neck joins the shoulder. If you stab through the trapezius muscle, you can reach the heart without any bones blocking the way. Messy, but by Roman standards, relatively quick and merciful.
Before the invention of soap, part of the bathing process was to cover your skin with olive oil, then scrape the oil off with an instrument called a strigil. Apothecaries collected the used oil, because gladiator sweat was believed to have aphrodesiac properties.
The emperor Commodus liked to dress as Hercules, and fight in faux gladiator matches. His opponents always carried unsharpened weapons, and were often drugged or crippled before the match. (He may have been crazy, but he was not stupid.) Despite what Hollywood depicts in The Fall of the Roman Empire and Gladiator, he did not die in the arena. He was killed by a gladiator, but it was either a lover’s quarrel or a paid assassination.
There’s a plaque on the outside of the Colosseum dedicating it to the Christians martyred there, but historians now think that probably none were. That tended to take place at the Circus Maximus about 500 m away.
It’s frickin’ HOT! That stone reflects a lot of sunlight on you, and when they warm up, they just bake you.
I saw a program on PBS or perhaps the Discovery Channel suggesting that they had some sort of sail-like fabric on long beams shading most of the seats in the Colosseum.