Down by the Anacostia River, children frolicked amid fountains on a plaza sparkling with sunshine and urban life. Families picnicked and strolled on the riverside lawns, watching the occasional kayaker row past, while couples on dates filled waterfront cafés at happy hour.

It seemed like a mirage to those who recall Washington, D.C.’s Navy Yard a decade or two ago, when vacant lots and forlorn streets had little to offer. But a decade-long population boom has brought new vitality to sleepy quarters around our nation’s capital. Construction is everywhere, restaurants are opening by the dozen, luxury condos are rising — and Jewish life flourishes anew in districts where it was dormant for a half-century.

Frankly, I’d always found the city a little, well, low energy. It had been a few years, and our visits always seemed to coincide with a long weekend or in August, when vacant streets and empty restaurants suggested a general evacuation as Washingtonians slavishly followed a government schedule. Washington is still very much a company town — the company being government, naturally. But there my husband Oggi and I were on a late-August weekend, waiting for a table at a restaurant on the trendy H Street Corridor.

All along H Street in the formerly neglected Northeast, check-cashing storefronts and pawnshops have given way to bistros, bagel shops and other signs of gentrification. H Street is also home to the new, Jewish-founded Mosaic Theater Company, which presents contemporary Israeli works alongside thoughtful fare aimed at the growing local audience — Jewish, yes, but also multicultural, sophisticated and culturally engaged beyond the next election.

H Street is in the renascent Northeast, but on a tip from local friends, we ventured to a part of the venerable Northwest quadrant that we’d long overlooked: Shaw, a historic ‘hood east of Dupont and Logan Circles. A century ago, the area around Mount Vernon Square teemed with Jewish and European immigrant life. Washington’s first YMHA opened here, along with numerous synagogues; Jewish-owned hardware stores, tailors, saloons and delis dotted the area around 7th Street.

Despite its central location and storied past, I’d never made the neighborhood a destination. But more than 20 new restaurants took root here just this year, most along the same boulevards — 8th, 9th, U — where Jewish merchants once plied their trades. Several small art galleries were a pleasant antidote to the sprawling museums further west, but what struck me most was the inviting sociability of Shaw: neighbors hung out on the stoops of their red and yellow row houses, and cafés all had the feel of a communal gathering.

Shaw was built by freed slaves, and long before its latest renaissance, the neighborhood was a hot spot for African-American culture. A century ago, the elegant Howard Theatre was a cultural nexus where locals flocked to hear Duke Ellington and other jazz luminaries; designated a national historic landmark, the theater had fallen into disrepair before its restoration and re-opening in 2012.

When we walked by the butter-colored building, signs advertised Jackie Mason and the Harlem Gospel Choir. Outside we saw a monument to Ellington, perhaps the neighborhood’s most famous resident. Nearby, young crowds flowed in and out of Atlantic Plumbing Cinema, a bar, lounge and movie theater in a renovated industrial building.

Shaw is one place to witness the evolution of black culture in what many locals affectionately call their “Chocolate City.” Another, famously, is the National Museum of African-American History and Culture, which opened in late September as the last and newest Smithsonian museum on the National Mall. We visited just beforehand, but by all accounts it is a stunning new attraction, and a popular one; plan carefully, since timed tickets are essential.

After the obligatory swing through museums and sculpture gardens, we headed down 8th Street toward the Anacostia. Rechristened the Capitol Riverfront, Washington’s old Navy Yard has a shiny metro station and hipsters tooling around on public bikes, which they dock at one of the new racks along the new, 12-mile Anacostia Riverwalk Trail.

The baseball team plays home games here at Nationals Park, which was the country’s first LEED-certified stadium when it opened eight years ago, and while the weather holds out, the Yard’s park hosts regular live concerts on the waterfront. Next door, the city’s favorite Jewish dining team, Wiseman cousins Nick and David, opened their latest boîte, Whaley’s, where the seafood comes with sweeping river views (no, it’s not kosher; not even close).

The waterfront is already lively, but much of the neighborhood is still under construction. In the shadow of new glass high-rises, blocks of neat rowhouses along empty sidewalks had an eerie, “Truman Show” feel, like a movie set waiting for its actors to arrive.

If the rest of Washington is any indication, it won’t wait for long.