BRENDAN SPIEGEL is a travel writer for the New York Times.

“SUPPORT OUR POWS. END TORTURE IN MAGHABERRY. RELEASE MARIAN PRICE,” scream the block-letter graffiti messages lining the 400-year-old stone walls that surround the historic center of Derry in Northern Ireland. Ascending the long staircase leading to the walls, I paused and looked back down the hill at a sign reading, “You Are Now Entering Free Derry.” Behind it, a somber mural depicted a gas mask-clad young man enveloped in a battle scene. At a glance, one might think I had stepped into a war zone.

In fact, this once hotly contested city is far from it. As I wandered under an archway and into the walled city, I was a bit taken aback by just how far.

The notes of a classical piano piece rang out from the First Derry Presbyterian Church, the clomps of an Irish step-dancing class echoed loudly through the narrow streets, and a chorus of enthusiastic buskers belted out tunes for passing shoppers. A rainbow-colored tourist trolley swung a busload of photo-snappers around the corner....