Thermopylae or Thermopyles are located in central Greece and is a place really close to the beach, to Maliakos gulf that is opposite the island of Evia or Εύβοια (in Greek). 

It became famous for the battle of Thermopylae in 480 BC, where an allied Greek military force under the command of Spartan King Leonidas defended the narrow street that connects southern with northern Greece. 

King Leonidas brought just 300 warriors with him, but the total number of defenders was higher, few thousands. The Persian King’s army, whose name was Xerxes, was quite bigger, since it was an invasion that its aim was to destroy Greece.  According to the Greek historian Herodotus its size was approximately 2 million of people (land and sea force). Event that many historians think that this number is a bit exaggerated, it may seem not, since the size of the Persian empire of that times was huge and contained armies from many different nationalities, even including Greeks from the today Turkish coast of Aegean. 

Allied Greeks were betrayed, and as soon as they realized so, Spartans asked everyone to leave and stayed there till all died fighting. 

Today there is a memorial at the area, and also some basic type of spa (the Thermopylae means Hot Gates in Greek) where you can enjoy through a rapid excursion.