Raines Law Room (flatiron location) is a great cocktail lounge / speakeasy with an upscale vibe. Check out their website depending on the night you're going because they take reservations at beginning of the week but not end of week / weekend.
The Flatiron Room specializes in all things bourbon plus they make great drinks and have a decent food menu. I second Sean's recommendation of Raines Law Room or it's sibling, Dear Irving- which is in Gramercy but close by.
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