1 Adam: Plato describes Atlantis as an island ringed by mountains, with a central plain 345 by 230 miles across.
2 Jamie: Why are you using Imperial units? Everyone knows metric is superior.
2 Adam: That sounds like a myth in need of testing!
3 Caption: Later:
3 Adam: Excuse me, sir, did you know that metric units are superior to Imperial units?
4 Man on street: Why no! I was previously unaware of this fact!
4 Adam: Myth busted!

I tried to find a reference to how large Plato said the entire island of Atlantis was, but as far as I can tell he never specified. All he did was describe it as a large island with mountains in the northern areas and around the coast, and a great central plain measuring some 3000 stadia long by 2000 stadia wide.

Although this comes to roughly the measurements in miles quoted by Adam above, the actual size of a stadion is the subject of some dispute between historical scholars. One stadion was equal to 600 Greek feet, but the size of a Greek foot is not known exactly.

A bit of calculation shows that Adam's measures correspond to a stadion being assumed to be about 185 metres, the so-called "Ptolemaic stadion".

And I am endlessly amused when I am watching the real world MythBusters, and they do some actual calculation, and it's all in units of feet and pounds and such. It's like something out of the Middle Ages.