The Thealla Mountains are an offshoot of the Ordero Mountain range in western Ivalice. The Thealla Mountains, solely in the state of Forriedor, are a significant obstacle to north-south travel in Ivalice. Until the mid-20th century, there were no safe routes of traversing the Thealla range, forcing travelers to go around them by land or sea, or over them by air. In 1976, the Diamond Coast Tunnel was completed through the Thealla mountains, connecting Londinium and North Forriedor with Koiwai and South Forriedor.