The Natonal Building Museum consists of a handful of exhibits spread throughout a massive building, the old Pension Bureau Building. It sits directly across F Street from Judiciary Square and (somewhat coincidentally, given the naming of Metro stops) the entrance to the Judiciary Square Metro station. If the trains aren't delayed, it takes about half an hour to get from our front door to the museum.

The exhibits are arrayed in rooms off the Great Hall, which is, in fact, great. The building is massive, occupying an entire city block between F, G, 4th and 5th streets. The hall itself takes up most of the interior space (its dimensions significantly exceed that of a football field), and at points it rises to more than 150 feet. If you go for that sort of thing, it's impressive.

Friday was dad's day at the museum. At least, that's what it looked like. By eleven in the morning, five dads, two moms and a couple were scattered about the Building Zone room, watching their children drive trucks, build with Legos the size of real bricks, play house, read books and pretend to be construction workers.

It is, after all, the National Building Museum.

This museum is popular among parents of young kids because it's free (there is a suggested donation of $5, but no one hassles you about it) and unlike most other museums (which cater to school-aged children), its kids room is set up for kids aged 2-6.

We were first in the room on Friday morning, arriving a few minutes before the scheduled opening time of 10 a.m. That's not a problem, because the museum is also an office building, and so its doors open at business hours. And if no one locked the doors to the Building Zone when they left the night before (a not-uncommon occurence, in my experience), it's open whenever you can get in the building.

Max and Sam busied themselves by arguing with each other about whose turn it was to play with the big dump truck. After some delicate negotations (involving the almost-as-big dump truck), they happily drove to neutral corners and began their own projects.

A few minutes later, a man and his son walked in. Richie (who is a month or two younger than Sam, my youngest) immediately went for one of the small dump trucks (whew!) and joined in the fun. His father walked over to me.

"Why don't they have a children's museum here?"

With that easy beginning, we took to talking about kids and D.C. and all sorts of things. Then he mentioned that he had just gotten back from a year in Iraq. He is a doctor, and he'd left his unit in order to get through his residency stateside.

I didn't say anything about the war. But he did.

"We shouldn't be there."

And that's it. Nothing else needed to be said. He told me that he felt like he'd abandoned his unit by leaving, but then again, the week he'd just spent with his son was more than enough to convince him that he could live with that guilt--no problem whatsoever.

We talked a bit about living in D.C. And about where he will be moving for his residency. Now that he will be "home" for three years, he and his wife are thinking about a second child. The usual sort of chit-chat, I suppose. Oh, and I asked him about his Nikon D40 camera, as my wife is looking at a digital SLR to replace our current digital camera. He likes the D40.

Then I had to attend to fresh disputes. Somehow, with all the other kids in the room, Max and Sam managed to interfere only with each other. Finally, Max and I sat down with a set of magnetic rods and balls--magnets on the ends of the rods and in the balls, so you can connect them at certain angles. Sam did something else, though I don't think I paid much attention to what--I've learned that if kids are playing quietly, it's always better to stay out of their way. Max created a fairly involved sculpture, which he first named "The Amazing Sculpture of the Sky." Then he reconsidered, declared his first title a "nickname" and re-dubbed the thing "The Amazing Sculpture of the Sun." We admired Max's work for about a minute. Then Sam came over and destroyed the sun (or the sky) in about five seconds flat.

Remarkably, Max didn't start wailing. He looked up at me and said, "Time to clean up." I was so flabbergasted by his measured acceptance of the destruction (lately, tends to go to tears when a single piece of mac and cheese drops from his plate) that I simply nodded. After a moment, I collected myself and thanked him for his mature behavior. He sort of nodded at me. 'Cause, you know, when your prize is lying on the floor in pieces, there's not much to do other than clean up.

We shouldn't be there.

Time to clean up.

Sometimes four words are all that need to be said.

Jon Worley is coming to favor the "Barney" school of foreign policy: "Clean up, clean up, everybody everywhere. Clean up, clean up, everybody do your share."