Wow, what a cool place! For a "hidden" bar it sure was busy the night that I went there with my wife and another couple. We had dinner first upstairs at The Bachelor Farmer (a must-visit) and since you can't get to Marvel Bar from inside the restaurant, even though it's in the same building and owned by the same gentleman, we braved the cold and icy sidewalk (scary, especially for such a high $$$ restaurant / bar) and walked down the exterior stairs. There are a couple of "entrances" to go through with someone there checking IDs, and they literally check everyone's IDs, even ours, and we're most definitely not looking like teenagers. That's great that they do that.
Once we walked down the stairs (I didn't see an elevator for physically-challenged folks, but, code-wise, there has to be one) we entered another world. The cloud pattern wallpaper, the sheets-of-plywood over the bar, the full-wall wine wall.. everything was so cool, so chic, so modern, so not like anything I've seen before. Which, isn't a good sign for my coolness..
They make drinks using only high-high-high end ingredients and everything is craft-specific, just like the Bachelor Farmer restaurant above. No "cheap" drinks here, but I didn't see anything over $14 which IS cheap for such a place. The four of us loved our selections and we were somehow lucky enough to snag a coveted round booth adjacent to the wine wall. It's worth the wait, otherwise you'll be left standing for an hour or two, which isn't all that bad in such a cool place.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.