La Frontiere Invisible (Les Cites Obscures) is a French picture book by Francois Schuiten and Peeters, published by Casterman in 2012. It is the first book in the Les Cites Obscures series, intended for young adults and adults. The book is coffeetable sized, with 136 pages and is illustrated. It belongs to various genres such as travel, adventure, romance, mystery, and art & culture. The book is written in French and has features of adult & erotic, pulp fiction, comics, and historical.