Thinking about House of Leaves recently made me revisit a train of thought I’ve often engaged in: Specifically, that there are a lot of architectural grandeurs that are avoided by players who use battlemaps because they’re difficult to map on a two-dimensional grid or table. (In fact, even if you don’t use battlemaps I suspect that there remains a subconscious aversion to such forms because most adventure prep still defaults to the presentation of a two-dimensional map.)
A significant example of this, for me, are large helical ramps or stairs:
Small spiral stairs, of course, are easy enough to include. But what I’m talking about are helical structures large enough that you could wage a massive melee on them. Perhaps one could do it with 3D terrain, but it seems far too complicated to render on a 2D battlemap. Which is too bad, because there’s a lot of cool stuff that can happen on a helix:
Awaking from a dream this morning, however, I realized that there was a way that one could map such a structure:

There are two tricks to using this map. First, a square is directly above the identical square two half-circles to the right (and below the identical square two half-circles to the left). Once you grok that, it shouldn’t be too hard to eyeball which sections of the ramp can reasonably see each other. (It will also let you easily calculate distance on the horizontal plane.)
Second, if the ramp has a 1:1 ratio of descent (i.e., it’s descending at a 45-degree angle), then horizontal distance on the map equates to vertical distance in the game world. For example, assuming 1 square = 5′:

The point marked B on this map is 120 feet directly below point A.
Of course, a 1:1 ratio of descent represents a fairly steep ramp. But you can set any ratio of descent you like and then just divide the distance. For example, if you had a more gradual ramp with a 1:4 ratio of descent you could just divide 120 feet by four and calculate that the vertical distance between point A and point B is 30 feet.
Once you’ve got both your vertical and horizontal plane distances, of course, you can use the Aerial Distances table on page 78 of Legends & Labyrinths to figure out the actual point-to-point distance. (Or you could calculate it using the Pythagorean Theorem, of course.)
It should be noted that this method isn’t perfect. Because each “half” of the ramp is horizontally inverted there’s a definite spatial distortion involved. For example, if you follow the outside curve of the ramp you’ll discover that it becomes the inner curve and then switches back to the outer curve. On 10′-wide ramp like this one the distortion is largely irrelevant (it can be corrected by taking a single diagonal move at each inversion point), but as your ramps get wider the distortion will become more pronounced.
But since I’m not modeling racecars seeking the inner track, I’m not too concerned.
More problematic would be creatures flying up or down through the space in the center of the helix. For this, you’ll want to calculate the vertical drop between each half-circle. (For example, on the map above with a 1:4 ratio of descent it would be 10′. Now you know that if the creature flies up 10′, you can move them into the identical position in the next half-circle.)












