Celadon City was a city referenced by Admiral Mordon in a password he gave to Maarek Stele. Several days after Mordin's death, Maarek received a letter claiming to be sent from his mother Marina Stele, asking her to write to her and to meet in Celadon City. Stele knew it wasn't his mother who sent the letter due to various discrepancies and after several unsuccessful attempts to get more information out of it was just about to give up when he realized the reference to Celadon City and used the password he remembered from Mordin to learn Mordin's last message to him.