The Boundary Stone’s main bar includes a stained glass version of the D.C. flag. (Fritz Hahn/The Post)

Located near Big Bear Cafe and Rustik Tavern, the homey tavern fills part of the old Sylvan Theatre near Rhode Island Avenue and First Street NW, an area that’s underserved in terms of places to meet up and grab a beer. That’s changing, thanks to three bartenders -- brothers Gareth and Matt Croke and Colin McDonough -- who live in the neighborhood and decided they wanted to work there, too.

Boundary Stone has a great feel. The comfortable interior is designed to create the illusion that it’s been there for years. The decor covers the checklist of trends: pressed-tin ceiling, polished concrete floors, exposed brick walls, reclaimed wood, exposed light bulbs and a heavy oak bar. There are some wonderful touches throughout, including a stained-glass rendering of the D.C. flag, some strategically placed TVs for Sunday football viewing, and a neon-lit CD jukebox packed with alternative, classic rock and punk albums. (Even better, it’s free.)

My favorite part is the glowing neon sign of the Sylvan Theatre lighting up the block again as it did before 1965, when the theater closed.

The alley next to the bar had been slated to be outdoor seating, but the owners enclosed the space to make a dining room. With the Dutch door that opens out onto the sidewalk, it reminds me of a stable. Weathered blonde wood, formerly used as snowfencing, covers the front and rear walls, and the space is full of cool little seating nooks.

Imperial pints of Guinness and 16-ounce tallboys of Busch Light share space on the beer menu. There’s also draft Dogfish Head, Yuengling and DC Brau, and cans from Avery, 21st Amendment, Brooklyn, Tecate and, uh, Stroh’s. Stroh’s is the cheap option, at $3; most other beers are between $5 and $6.

Menu-wise, Boundary Stone welcomes folks looking for Americana comfort food -- deviled eggs, fried pickles, spicy nuts, beer-can chicken made with DC Brau -- and it’s sure to appeal to vegetarians and vegans, too. There’s hot honey “wings” of seitan and fantastically crunchy arancini with fresh veggies mixed in its fried risotto.

Boundary Stone might not always be as crowded as it has been this week, but the packed house is a good sign for both the bar and the neighborhood.

The alley adjacent to the Boundary Stone has been enclosed and turned into the pub’s dining room. (Fritz Hahn/The Post)