What Harmony's people call the Ruins of Larris is actually an outpost built by the Lanteans. There, they researched and developed Drone weapon technology, and used the planet and surrounding forest as their testing ground for mini-drones. These devices were controlled by the thoughts of the wearer of a pendant that served as a passkey to a control interface similar to a control chair.
The people of Harmony's planet have incorporated the ruins into their mythology. Before a woman can become queen, she must go on a rite of passage in which the destination is the Ruins of Larris. The soon-to-be queen must return a pendant to the ruins and place her hand on a pedestal. If the pendant then glows, she is the true queen of her people.
Dr. Meredith Rodney McKay, a member of the First Atlantis Reconnaissance Team and the Chief Science Officer of the Altantis Expedition mentioned reading about the outpost in the Atlantis database and his team had been looking for it for two years. (SGA: "Harmony")