Michael Schulson has upped the cool factor next door to his modern Asian small-plater Sampan.

In what had been a gay porn theater, he has built the two-level Double Knot (120 S. 13th St., 215-631-3868), opening Tuesday, Feb. 2 in Philadelphia's most densely populated restaurant area (Tredici, El Vez, Vintage, Charlie was a sinner., Zavino, Barbuzzo, Capogiro, Lolita, Jamonera, Zio's Pizza, Raw, Bar, Time, etc.).

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Double Knot's ground floor is a tastefully appointed, moderate-energy coffee bar, whose java is overseen by Elixr Coffer Roaster's Evan Inatome; it opens at 7 a.m. with a full line of drinks and pastries. Inatome invested in low-profile Modbar coffee-dispensing equipment.

Lunchtime brings Vietnamese fast-casual for eat-in and takeout; for $7, you get a choice of steak, chicken, pork, meatballs, tofu or shrimp over broken rice, rice noodles, cabbage salad or as a bahn mi. Nighttime, it's all bar. (The cocktail list includes coffee drinks; try the espresso-tini.)

But psssst. Walk through the coffee bar, past the settees, bookcases, tufted banquettes and old mirrors, and walk through a door at the back. Take a turn and head down a brick-lined staircase.

Your eyes adjust. Pop! You're at a sushi counter. Chefs are bustling. A robatayaki grill sizzles at the far end.

Look further, and you'll see a series of small dining areas, plus another bar.

Double Knot is a coffee bar and (after 5 p.m.) a subterranean Japanese izakaya.

Where Schulson's Izakaya at the Borgata in Atlantic City is modern and casino-styled, Double Knot has a much more urban, industrial, and literally underground feel.  (Rohe Creative did the design.)

It's also sprawling. The ground-floor coffee bar takes up a city storefront. Underground, however, DK extends beneath both the coffee bar and Sampan. (The best seat in the house is a pink banquette for six to eight people tucked into a corner.)

The menu includes plenty of robatayaki - almost 40 items including gizzards and other offal, lobster, lamb chops and chicken breast. There's a full sushi selection with specialty rolls created by executive chef Kevin Yanaga. The food is small plates as well as items for two: rice cracker and hearts of palm salad, rib eye with honshimiji mushrooms, seabass with soy truffle and charred snap peas.

Hours are 7 a.m. to 9 p.m. Sunday, 7 a.m. to 10 p.m. Monday and Tuesday, 7 a.m. to 11 p.m. Wednesday and Thursday, and 7 a.m. to midnight Friday and Saturday.

Schulson and fiancee Nina Tinari, incidentally, are about to start construction of Harp & Crown, a casual American restaurant on the 1500 block of Sansom Street.