Elassona is a town and a municipality in the Larissa regional unit in Greece. During antiquity Elassona was called Oloosson and was a to…Elassona is a town and a municipality in the Larissa regional unit in Greece. During antiquity Elassona was called Oloosson and was a town of the Perrhaebi tribe. It is situated at the foot of Mount Olympus. Elassona is bypassed by the GR-3.