Attire is festive casual. Please wear whatever makes you feel comfortable, warm and confident. For those unfamiliar with January in NYC, dressing in layers can prevent you from shivering outside and sweating inside.
There are a couple steps down into the lounge area, where dinner and drinks will take place. There is a full staircase to the cellar and dance floor.
There's an abandoned Long Island Rail Road tunnel beneath Atlantic Avenue a block from the venue. When open, it ran for about 2,517 feet between Columbia Street and Boerum Place. You can read what Walt Whitman wrote about the tunnel here: https://en.wikipedia.org/wiki/Cobble_Hill_Tunnel#cite_ref-CB_10-0