What is the pillars of Hercules?

The Pillars of Hercules refer to two mountains that flank the entrance to the Strait of Gibraltar: the Rock of Gibraltar on the European side and Monte Hacho on the African side. In ancient mythology, they marked the edge of the known world and were associated with the hero Hercules, who was said to have placed them to signify his journey. The phrase is often used to symbolize boundaries and exploration beyond the known territories.