Sorry all my questions are about heroica, but this needs to be easy so that I can build in a few mins. I will make gladiator micro figures as well, if someone can make a Lion too!
You're going to need a lot of pieces. And I don't know if you are talking about making it for your game boards or for your minifigures. I, the LEGO know-it-all, will help you out. I have made a ton of things, including a LEGO to-scale tennis court. That was fairly easy and I made it in about 3–4 hours.
So, if you want to make an arena, you first have to make a square- or circle-sized, box-like base with walls. Make four walls and put them all together as if you were making a house.
Then, make some stands. These will be supported by poles or stacked bricks ot have the height over the wall. This will take a lot of pieces, but very basic ones. What you want to do is use long skinny 2×12 or 2×10, or any longer plank, and 2×4 bricks, and you will want to build some seats or bleachers with those. I will upload a pic of those soon.
Then, you want to kind of make a roof over those bleachers. And of course you also want some entrances and maybe a gate or tunnel. Then you can use the bear from LEGO forest police, make some chariots, and have fun.
Let's assume that the Heroica figures are exactly half the scale of the normal LEGO minifigure. That would be roughly 1:100. At that scale, 1 meter would be roughly 0.75 studs long or the height of a standard LEGO brick.
Now let's convert the Coliseum dimensions:
To calculate the real dimensions of this LEGO construction, let's remember that a brick is 9.6mm high and the distance for 1 stud is 8mm (= 1 stud radius + the distance between two studs).
Using these values we get:
@Those two distances are calculated by multiplying 6.4mm with the number of studs, and then adding 1.6mm for the last little bit of beam left after the last stud.