I'm working on a map of Roche's estate in Madripoor, and a thorny terrain problem has come up. The estate is on a cliff side by the ocean, so part of the map consists of the water below. By necessity, the rest of the map (the estate itself) is elevated. The estate is also surrounded by a stone wall thick enough to walk atop. That's where I'm having difficulty. If I make the wall EBT, most figures can't get on it. What I'm wondering is if there's a technical definition for "building" in Heroclix. I'm thinking that if I define the wall as a "building", I can make the wall clear elevated terrain just like the ground surrounding it, but the various references to "the edge of a building" in the rulebook will cause it to behave in a somewhat logical way (e.g., knockback will send figures off the wall instead of slamming them into its edge from the "inside", LOF from the wall to the ground won't be blocked by the thick black border, etc.).
If the building idea won't work, can anyone think of something else that will? My criteria for a properly functioning wall are:

1. All figures can stand on it.
2. Ranged combat down from and up to the wall is possible.
3. Wall segments can be destroyed.
4. Knockback into the wall stops movement (causing knockback damage would be nice, but it's not really important), while knockback to figures standing on the wall will knock them off.

It's YOUR map. Keep in mind that "elevated blocking terrain" becomes a "building" by simply providing some way for grounded figures to get up onto it. Stairs, perhaps. Or a ladder in one square. Or even a pile of rocks that a non-Leaping/Climbing figure could scale to get up atop the wall...

...thus making it a "building". It would then be subject to the ordinary rules in the book, yes? This would seem to match your criteria.

The only thing I could argue about would be that it would be necessary to destroy each wall segment TWICE to completely destroy it, since it's going to be at least one square thick, so you'd have to blast the ONE thick black line (north side of the wall, say) followed by the OTHER thick black line (south side of the wall.)

The problem with just sticking a ladder on EBT is that figures without L/C or flight still can't legally enter the square. I could change it to elevated *clear* terrain, but then the figure who enters is going to be boxed in by the thick black border as if he were, well, in a box. I'm wondering if I can get that "box" behavior to change by defining the wall as a building; if I can, I'm sure I'll have to change the square to clear, rather than blocking, terrain.
You're right about breaking down the wall, though, and I hadn't even though of that problem. Wouldn't be disastrous to have to hit twice to break down the wall, but that's another thing I'd like to fix. If only the EBT rules weren't so screwed up....

One thing you might not have considered, if you can destroy the wall, will that leave people on the wall stranded because they can no longer reach the way up/down? Besides, on an outdoor map, no terrain can be destroyed.

Actually, making the wall elevated clear terrain solves the problem of stranding figures, because anyone on the wall would be able to walk down to the ground through the rubble (since the rubble, ground and wall are all at the same elevation). In addition, there are a number of ladders along the wall. Mechanically convenient, and not that unrealistic; I figure the wall's only about 7 feet tall, so if somebody blasted a chunk of it out, you'd probably be able to climb down the rough opening pretty easily.
Any other opinions on defining the wall as a building?