Cement/Concrete.

[TatteredShoeLace]

Rev, how do I flood my roman ampititithiem...i mean the colleissis...how do I put boats in my arena and lions?

[Revanael]

They never, at least according to all historical knowledge, flooded the Collisseum itself. Some smaller amphitheatrum may have been used for mock naval battles, though... nobody's truly certain.

[TatteredShoeLace]

Really? I could have sworn they actually could flood the main one...don't kill my dreams Rev

[Revanael]

There's no signs whatsoever of water -and if they had, there would be some sign, even after all this time. The cells underneath would have made it highly impractical anyway.

[Doodle_Jack]

Well, a documentary on Discovery Channel claimed they did flood the collosseum in those times. But they also said they probably just did it once or twice when the thing was just opened. It was too expensive and too hard to flood the place regularily. Anyway, it was possible.