The Rainbow Warrior, the yacht used by environmental group Greenpeace, is currently docked at Flisvos Marina in southern Athens.
Members of the group are conducting free guided tours of what is thought to be one of the greenest ships in the world.
People can visit the vessel from 10 a.m. to 7 p.m. today or between 10 a.m. and 2 p.m. and 4 and 8 p.m. on Sunday.
The Rainbow Warrior was completed in 2011 and runs primarily on wind power.
It was built with money donated through a crowdfunding drive. More than 100,000 people contributed to the vessel’s construction.