[bert]

It looks pretty much like Greek to me.

Delta Theta Epsilon ?

[RightWhale]

tagging by those radical Pythagoreans

gthzph

[SunkenCiv]

Here are Delta, Theta, "Xi", Epsilon:

Here's the inscription:

Not much of a match, because the Greek alphabet is nearly two thousand years younger than this inscription may be. If graffiti, and postdating to the medieval opening of the ancient entrance, what language? what script? what's it say?