The Battle of Thermopylae where king Leonidus and his "300 spartans" (it was actually a few thousand of a coalition force) held off the Persian invasion of Greece.

The plan was to use the narrow mountain path to pit a few of tgeir well trained soldiers against a few of Persias rank and file. The idea being a few well trained soldiers could take out a lot more rank and file if they didnt have battle tactics to worry about.

What caused Leonidus to lose that battle is an alternate route through the mountains that let the Persians flank the Spartans and probably totally destroy them.

What's mind blowing is this was hundreds year old history when Rome tried the same thing.

This one spot is famous for losing battles and ancient people loved choosing this battleground and then losing