Simplify the following text for a Grade 9 native English-speaking person.
Original: His most iconic images are his woodcuts of the Four Horsemen of the Apocalypse ( 1497 â `` 1498 ) from the Apocalypse series , the Rhinoceros , and numerous self-portraits in oils .
Simplified: His woodcuts , such as the Apocalypse series ( 1498 ) , retain a more Gothic flavor than the rest of his work .