The other day, a friend asked us an interesting question: Why does Vice President Joe Biden have so many meetings at the US Naval Observatory?

You see it on his schedule all the time: 9:30 a.m. VP Joe Biden to meet Secretary of State Clinton at Naval Observatory; 11 a.m. VP Joe Biden greets National Spelling Bee champions at Naval Observatory; 12 noon VP Joe Biden tips pizza delivery guy at Naval Observatory; and so forth. (Yes, we made that last one up.)

We liked the question because it illuminated the divide between what Washingtonians know as a matter of course and what the rest of the nation doesn’t. Ask pretty much anybody who’s worked for or around the federal government and they’ll shrug and tell you the answer: because that’s where he lives.

Technically speaking, he lives at 1 Observatory Circle, a Victorian home that serves as the US vice president’s official residence. The house sits on a high point of the Naval Observatory grounds, a big swath of open land just north of the British Embassy on Massachusetts Avenue. It’s hard to drive through upper Northwest D.C. without skirting it.

Didn’t know the veep had a government home? What did you think – that Biden sleeps on a pull-out sofa in the West Wing and raids Obama’s fridge when POTUS is busy with Speaker John Boehner?

Vice presidents have had their own residence since 1974. Congress ordered the move mostly because it was getting very expensive to outfit each new VP’s private home with security and communications equipment.

The house was already government property. It was built in the late 1800s as the home of the Naval Observatory’s superintendent. In 1923, the Chief of Naval Operations booted the superintendent to lesser quarters so he could have the house. It’s quite nice, actually.

A couple of years ago Biden mentioned to a reporter that he’d been shown a secret bunker in the basement. His spokesman later said he’d misspoken. Maybe he’d really seen a secret passage of a different sort – one that leads to the telescopes the Navy still operates on the grounds.