Liberio was a Marleyan city that contained an internment zone, a designated area of land for Eldians on the mainland to live in. It was the hometown of many of the Warriors as well as Grisha Yeager. It was destroyed during Eren Yeager's Rumbling, though many inhabitants were able to escape the city before its destruction.
History: At the end of the Great Titan War, King Karl Fritz and many Eldians settled on Paradis Island, fleeing from the mainland war. However, some Eldians stayed behind on the continent were overtaken by Marley, the enemy nation. Rather than slaughtering the remaining Eldians on the continental mainland, the nation of Marley chose to isolate the Eldians into designated internment zones.
Story: During the Wall Rose invasion when the Survey Corps recruits battle the Titans at Utgard Castle, Reiner comes close to death by a Titan and fears for the end of his life before he is saved by Bertolt. At this time he strengthens his will, filled with determination to return to his hometown. He shares his resolve with Bertolt, who understands the true meaning of what Reiner says and agrees with his hopeful words.
Source: Liberio, available under CC BY-SA 3.0.