Possible Clues:

• Place oddly not one found in map collection?
• Mythical island: Santa left it out!
• Titan carries books on island, a legendary one
• Archaeological adventure novel by David Gibbins
• Lost land from biblical books, one in mountain range
• Island not traced? It's given name, turning up in map book
• Shuttle that docked with 14-Down
• Down under island?
• Legendary lost city
• Place having submerged tin works appearing in map