What are the "D" symols in Realm of the Ice Witch?

Ice Witch is my first Dungeoneer game, and I tried a solo outing.
Two of the first ten map cards out have a large white capital "D"
in a striped gray circle. I searched the rules and the online pdf for v2.3,
but I can't find any reference to these symbols.

What do they mean??

Thanks....Alan

Those are Sewers. See the v2.3 rules under Alternate Exits.

You can move from a sewer to another sewer of the same letter (A:A, B:B, D:D) for 1 movement point.

First, I do want to thank Thomas (the designer) for personally answering my question about what the "D" markings on map cards in Ice Witch mean.

However, I feel I have to mention that the only explanation that a pdf-search for the term "sewer" returns is a self-referential one that says basically "sewers" connect to other "sewers" of the same marking. Nowhere does it tell us that a sewer might be indicated by a large letter in a circle on a map card, at least that I've found.

So, there are large (human-sized) sewers in the middle of arctic forest
clearings....Hmmm. While I'm willing to buy this concept for an urban set,
or a dungeon set, it seems to tax my "willing dis-belief" in the middle of a
tundra forest.

The one place I've seen this "effect" before is in Tikal, where placing a new "tent" suddenly makes movement from the generic/common starting tent to your new one only one move factor.

There, it's explained away as "now you know the short-cuts". Perhaps something similar would be appropriate here, as someone building convenient sewer sytems in Arctic or Desert conditions seems a little hard for some players like me to put aside and enjoy the game.

I truly wanted to get into this system - I'm looking for a 1-2 hour solo dungeon/adventure system, with meaningful decision-points and
non-trivial, yet not-all-consuming combat parts. Dungeoneer looked the part, but now I'm not so sure.

Again, I do thank Thomas for a direct response.

A

Isn't the symbol for sewer explained on the Symbol Reference card?

I do think having the symbols directly next to the descriptions in the rules is probably a good idea.