A volunteer checks in on some of the feathered residents of the Garuda Aviary in Poolesville, Md. (Emily Pearl Goodstein photos)

Underneath, or next to, or just a little out of the way from all the iconic places in D.C. are the hidden gems — the spaces that many of us never get to see. In their new book “No Access Washington, DC,” Beth Kanter and photographer Emily Pearl Goodstein curate a tour of the city’s little-known haunts, like the cavernous, graffiti-ridden basement underneath the Lincoln Memorial and the Finnish Embassy’s invite-only sauna. “I really think of it as a love letter to D.C. and the people who live here,” says Kanter, who’s called the city home since 1991. “So many good people here are part of these places, and part of preserving and maintaining them — often with little or no recognition.” Here are a handful of the 45 hidden treasures profiled in the book, which Kanter and Goodstein will discuss on Monday at Sixth & I.

Sixth and I, 600 I St. NW; Mon., 7 p.m., $12 ($30 including book).

Former Iranian Embassy

Most people who stream past the former Iranian Embassy on Massachusetts Avenue have no idea it was abruptly shuttered in 1979 and now “stands frozen in time.” Kanter spoke with photographer Eric Parnes, one of the few people who’s been inside the building since it was sealed off when the U.S. and Iran ended diplomatic relations, and he described it as a tomb. But in its former life, in the 1960s and ’70s, the embassy “was known for these parties that would last into the night, with the champagne flowing,” Kanter says. “It had these elegant, beautiful rooms with gorgeous interiors, and there was a fountain in the courtyard that looked magnificent.” The Vienna Convention on Diplomatic Relations requires the U.S. to maintain the property, so snow is removed and the grass is cut, Kanter says, but presumably “nothing has been done in the interior” since it closed.

‘Mini Mon’

“Oh, this one is wild,” Kanter says of the miniature Washington Monument that’s tucked underground just 150 feet south of the real deal. She and Goodstein affectionately dubbed the concrete replica “Mini Mon,” but it’s officially called the Elevation Obelisk. In 1898, the U.S. Coast and Geodetic Survey installed the benchmark to help gauge how much the monument was settling into the ground; it’s 13½ feet tall and 3 feet wide at its base, and it’s now concealed by a manhole cover that hundreds of visitors likely stomp over every day. During her research, Kanter discovered a decades-old newspaper photo of “two women picking up the cover of the utility hole themselves, and peering inside.” She laughs as she recalls the image, noting: “Obviously, now it’s under lock and key.”

Garuda Aviary

In rural Poolesville, Md., 30-odd miles outside D.C., there’s a Buddhist temple and monastery where one might reasonably expect serenity. But on approach, the sharp shrieks of 50 or so parrots pierce the silence. Garuda Aviary, on the campus of the Kunzang Palyul Choling Buddhist Temple, takes in neglected, abused and abandoned parrots — typically surrendered by people who didn’t realize how complicated raising the birds can be, Kanter says. Many of the parrots suffer from an anxiety disorder that causes them to pull out their feathers, leading to blood loss, nerve damage and other health problems. The aviary’s volunteers “take care of them and keep them for life — and parrots live a long time, so that’s a big commitment,” Kanter says. “We met one who was 50 years old.”

Embassy of Finland’s sauna

“It’s the hottest invitation in town,” Kanter says, and she’s not kidding: Once a month, the Embassy of Finland invites a handpicked group into its ground-level sauna. The gathering pays homage to the Finnish tradition to use a sauna at least once a week beginning in toddlerhood; most homes in Finland have them, and in the past, Finnish women even gave birth in the hot chambers. The embassy’s Diplomatic Sauna Society hosts the Friday night celebrations, which often last past midnight. “There’s a beautiful lounge and a bar with signature cocktails,” Kanter says, and upon departure, attendees receive a “sauna diploma” commemorating their unique experience. While the embassy won’t reveal exactly who’s participated, the invite list has included big-name musicians, writers and Hill staffers.

Lincoln Memorial undercroft

Underneath the popular monument, there’s a three-story, 43,800-square-foot basement that Kanter describes as “Hogwarts meets Luray Caverns with a dash of deconstructed cathedral kind of vibe.” Though she was vaguely familiar with the undercroft before actually exploring it, “I had no sense of how truly majestic it is,” Kanter says. “It’s huge, and incredibly quiet. It’s kind of a metaphor for the whole book, looking at what’s holding up some of D.C.’s most iconic places.” She was particularly wowed by the vintage graffiti, etched into the concrete walls by the construction workers who spent eight years building the memorial, starting in 1914. “The aesthetic matches the time — big moustaches and bowler hats, a woman smoking a long cigarette. It’s quite artistic.” The undercroft is closed to visitors, but the National Park Service is considering plans that would open it to the public for tours.