Thermopylae

[Jona Lendering]

How exactly do we know that the water came up to that road?

I have little to add to the preceding message, except that Herodotus makes it very clear that the strip of accessible land was very narrow. Immediately north of the road, even today the country is substantially lower. You can see the ancient coast line and distinguish it from the later deposits. The deposits can be radiocarbon-dated if there are traces of organic material.

So we have three of evidence: the line in the landscape that divides the old and the new land; the description by Herodotus; the dating of the deposits.