Months after we visited the Spy Museum, my 11-year-old and I still like to test each other's powers of observation. We'll be standing in a store or other public place and look around for signs of "hostile surveillance, security systems, and unexpected risk or unlucky breaks." We're putting into practice some tips we picked up at the museum, in a section called "Tricks of the Trade," where interactive monitors teach you what to look for, when it comes to suspicious activity. This tradecraft area is the first you come to in the museum, after you've seen the 5-minute briefing film, and it's easy to spend a lot of time here. In addition to the surveillance games, the section displays trick equipment (such as a shoe transmitter used by Soviets as a listening device and a single-shot pistol disguised as a lipstick tube) and continuously runs film in which spies talk about bugging devices and locks and picks. You can watch a video that shows individuals being made up for disguise, from start to finish, and you can crawl on your belly through ductwork in the ceiling overhead. (The conversations you hear are taped, not floating up from the room of tourists below.)

Try to pace yourself, though, because there's still so much to see, and you can easily reach your personal limit before you get through the 68,000-square-foot museum. The next section covers the history of spying ("the second oldest profession") and tells about famous spymasters over time, from Moses; to Sun Tzu, the Chinese general, who wrote The Art of War in 400 B.C.; to George Washington, whose Revolutionary War letter of 1777 setting up a network of spies in New York, is on view. You learn about the use of codes and code-breaking in spying, with one room of the museum devoted to the Enigma cipher machine used by the Germans (whose "unbreakable" codes the Allied cryptanalysts succeeded in deciphering) in World War II. An actual Enigma machine is displayed, and interactive monitors allow you to simulate the experience of using an Enigma machine, while learning more about its invention and inventor.

Much more follows: artifacts from all over (this is the largest collection of international espionage artifacts ever put on public display); a re-created tunnel beneath the divided city of Berlin during the Cold War; the intelligence-gathering stories of those behind enemy lines and of those involved in planning D-Day in World War II; an exhibit on escape and evasion techniques in wartime; the tales of spies of recent times, told by the CIA and FBI agents involved in identifying them; and a mockup of an intelligence agency's 21st century operations center. You exit the museum directly to its gift shop, which leads to the Spy City Café.

While you may look with suspicion on everyone around you when you leave the museum, you can trust that what you've just learned at the museum is authoritative: the Spy Museum's executive director was with the CIA for 36 years and his advisory board includes two former CIA directors, two former CIA disguise chiefs, and a retired KGB general.

The International Spy Museum has been immensely popular ever since its mid-2002 opening, which translates into long lines for admission. Consider ordering advance tickets for next-day or future date tours through Ticketmaster (tel. 202/432-SEAT), which you can pick up at the Will Call desk inside the museum. You can also purchase advance tickets, including those for tours later in the day, at the box office.