Secret Mission 11 -- Point of Impact | Devil May Cry 4
The Lucifer weapon is needed to reach this one. After killing the first batch of Basilisks, start up the mountain ledges until you reach a set of stairs that lead up into the left corner of the screen. With Trickster toggled and Lucifer equipped, stand about midway up the stairs, jump to the right, use Air Hike, Sky Star, then attack with Lucifer and you should land on the secret ledge.
This video is from our unofficial game guide. You can view the full guide here