Those guys aren't wearing pants," observed my 11-year-old granddaughter, Olivia. I was delighted she had noticed. 

In fact, we were surrounded by statues of pantsless, grim-faced Roman soldiers - all concealing their lower bodies with large shields - looking down as they have for more than 100 years at Union Station in Washington, D.C.

We were eating lunch at the Center Cafe, perfectly located at the center of the station's 96-foot-high vault. Olivia's sisters Emma, 15, and Madison, 14, glanced up from their panini to look. It was a perfect grandfather moment. 

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"You see those shields?" I asked. The girls nodded. "They weren't originally there. If you were to take a good look behind those shields from the side, you'd see that each one of those guys is naked."

The girls' panini-filled mouths dropped open.

I raised one eyebrow. "And I mean … totally … naked."

"You're making that up, Papa!" said Madison, who knows me too well.

My wife, Carolyn, squinted suspiciously.

"You mean 'nude'?" she said.

"Yeah, Papa, nude??" Madison echoed. 

I smiled smugly. I'd done my research.

"Yep. They were carved naked, and the officials were mortified. They ordered the sculptor to put shields in front of them all."

The girls munched away, gazing thoughtfully as I smiled across the table at Carolyn. 

"Chalk one up for Papa! " I told myself. 

This lunch was a rare sitting-still moment during a whirlwind two-day visit to the nation's capital. The girls had flown in from New York, and Carolyn and I had driven in from our home in Delaware. We met them Friday night, right at their gate at Dulles International Airport (an arrangement that must be made in advance with the airline). As the five of us walked out of the terminal, I told the girls of a wondrous time when anyone could walk into any airport, stroll up to a gate and meet their loved ones as they got off the plane. 

"That's crazy," said Emma, the most cautious of the three. 

We drove into D.C. and checked into the Kimpton Madera Hotel (conveniently located near the Dupont Circle Metro but, most important, featuring large rooms with two queen beds, a pull-out couch and bunk beds). 

Saturday morning, after a quick breakfast at a Dupont Circle bakery, we were off for the U.S. Capitol Visitor Center — a grand, sunlit interior space at the foot of the Capitol Building's east front. The girls felt excitingly dwarfed by a full-size plaster version of the Statue of Freedom, which tops the Capitol dome. 

"She's wearing a bird for a hat," said Madison, the granddaughter with a flair for fashion. 

"It looks like the bird pecked her eyes out," added Olivia, the one with a taste for the macabre. 

We wanted to tailor this weekend with something for each girl, so for Emma, the bookworm of the family, we headed to the Library of Congress - which is linked to the Capitol via a tunnel under First Street NE.

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From a balcony overlooking the library's main reading room, we marveled at the dome and statues of literary figures. We peered into a display case at a copy of the Magna Carta. I looked with anticipation at Emma, who seemed unimpressed.

"Is there anyplace I can actually look at a book?" she asked. 

A fair question with a good answer: Down a long hallway, we found the Young Readers Center, where kids can read their favorite books, and galleys of upcoming ones. Emma's blue eyes lit up as she selected a copy of a yet-to-be-published novel. While I scoured the shelves for Shel Silverstein and Dr. Seuss, and Madison ran her finger along a braille edition of a Harry Potter book, Emma sat on the floor, immersed in her find.