The simplest answer is likely one you won't like.
For in-person maps, nothing is better than the large vinyl maps that can be purchased at almost any large gaming store. It is obviously labour intensive to copy an existing map into larger scale, or create your own. But with the right set of markers, you can reuse it for a long long time.
I have also created my own 1 inch hex grids on letter sized paper, and of course, have large chart paper for squares. If you really want a set piece room, create it on paper, and you can introduce it any time, anywhere, in the dungeon.
If you want to draw maps ahead of time, the best solution is Gaming Paper (Amazon.com), or the more affordable (and just as good) Enormous Pad of Graphing Paper, which you can easily get at Staples. Draw ahead of time on expensive vinyl mats, and they're ruined after a handful of uses.