Half-Life 2 Hints

In the Chapter Anti-Citizen, Freman can reach the rooftop of the building blocked by some rocks on its stairs. After D.O.G. hops onto the dropship, crouch jump onto the sofa and Freman can jump past the rocks. Bring a box or similar object to act as a platform. It is barely possible to reach the roof of the building -- there's nothing there, but it's a little hidden area.