If you're talking about the uk, no. You can fly 400ft above the natural terrain, it explicitly excludes man made structures. So, for example, you can only fly 400ft up the side of a transmitter mast or tower block that is 1600ft high. If you where to launch from the top of a 400ft high building, then you can only go down, not up. You can apply to the CAA for additional permissions to carry out that sort of flight tho'. There's a thread running in the general discussion topic on this.