The Green Ridge Mountains were the sole mountain range of the continent of Atlantis. They began in the northern most tip of the continent and ran southerly, effectively dividing the continent in half.
Historically, the dense terrain of the Green Ridge Mountains made overland exploration of Atlantis somewhat difficult, but by no means impossible. Indeed, for the most solitary of Atlanteans the daunting terrain allowed many settlements to develop in relative isolation from those found on Atlantis' respective coastlines. The first known human to cross the Green Ridge Mountains on foot was Richard Radcliffe, the younger son of Edward Radcliffe, the Founder of Atlantis.
Nonetheless, Atlanteans generally preferred traveling by ship around the continent rather than over it.