The Underground Railway Ruins are an ancient Icarian railway in Grandia. The railway is located underneath the J-Base and lead to the heart of Icarian City. Although the railway and trains are no longer operational various elevators are still functional.
In an attempt to stop the Garlyle Forces from reviving Gaia, Justin, Feena, Rapp and Liete head towards the J-Base. Upon arrival they find that Colonel Mullen has started a mutiny against his father and the soldiers are fighting against the revival of Gaia.
The party head towards the TACOM Center and find an injured soldier inside. The soldier tells you to follow Mullen through the secret passageway behind one of the walls. In the passage, Justin and the party find a wounded Mullen and Leen. Mullen demands to know why Justin handed over the Spirit Stone to Baal when it would lead to the destruction of the world. He then tells Justin to prevent Baal from reviving Gaia.
The party head down a nearby hole which leads to the Underground Railway Ruins, the party travel through various train wrecks and eventually arrive at a functional lift that takes the party to Gaia's Ovarian Chamber. The party confront General Baal who has become one with Gaia, he attacks the party as they attempt to stop him. After the party defeat Baal, Gaia is revived and its roots burst out from its cocoon. Leen arrives and uses her Icarian wings to protect the party and bring them to the Lyonlot.