The monument stands opposite the historical hill of Kolonos and represents Leonidas in full armour. It was designed by B. Phalereus, and was erected in the 1950s at the expense of Greeks living in America.

The monument was built to commemorate the battle at Thermopylae, and is located at the centre of the pass, where the final phase of the battle took place, as is attested by the accumulation at the foot of the hill of iron and bronze spearheads dated to the 5th century B.C. Members of the Amphiktyony erected on the hill a stone statue of a lion in memory of the deceased warriors, with an epigram written by Simonides, but the monument is not preserved today.

A restricted excavation on the hill of Kolonos, in 1939, revealed fortification works of several periods, Roman and Byzantine graves, and ruins of Byzantine buildings.