I know of three spots to get past the "invisible barrier" that the designers use to stop you. In East Freeport, by the entrance to the Thieves Way, if you jump onto the wall, then onto the building, you can climb all the way to the top, or jump across to the other side of the area, where there are 3 spots where you can jump out of the world. Being on these buildings kills the guard's pathfinding(for people from Qeynos).
In Qeynos Harbor, coming from the Mariner's Bell, head towards the Scribe Shop. The building straight across the bridge is our next target. Head inside, up to the top, and out onto the balcony. Jump onto the railing, then onto the roof of the building. If you go too high up onto this roof, you will fall through the building(including the prefiously-tangible floors) and out of the world. You can also jump across to the other building, but going too high on this building will result in the same thing.
The last place I know does not result in falling through the world, but would probably screw up guard pathfinding as well. In the Willow Wood, behind the building next to the bank, there is a ramp up to an area with a bear and some npcs the other way. You can jump from this elevated area to the beams sticking out of the building. then, jumping from beam to beam, going to the right, you will have to jump around a corner that looks like this from above: _|‾. After jumping around this corner, run straight into it, and you will crouch under and through the invisible barrier. From here, you can jump across to the top of the bank. This is where I set my bindpoint
