Last October, the Marvelous María Beatriz and I finished watching the final season of Derry Girls, which ends with the vote in 1998 for the Good Friday Agreement. This coincided with my finishing Say Nothing: A True Story of Murder and Memory in Northern Ireland by Patrick Radden Keefe, which chronicles some of the years in Derry Girls.

One would think that after 25 years the conflicts might have softened, but as part of our Irish sojourn from July 28 to August 15, we traveled to the places talked about in both works and learned from our eyes and ears and the pound of our feet on the pavement how active the divides still are in Northern Ireland, where the British are still resented by the Catholics and the Protestants have their heels dug in very, very deep.

In Derry (or Londonderry, depending on allegiances), the Bogside Murals, which depict the ongoing struggle for Catholics about remembrance and justice, unfurl in an area that has been at odds with British and Protestant rule for centuries. This includes a siege in 1688-89 when James II tried to starve Derry's inhabitants into submission and the declaration of a Free Derry in 1969, when Irish nationalists fought back against the Royal Ulster Constabulary, only to be smashed themselves in 1972 during Operation Motorman, when the British army regained control. And, of course, the most infamous event of them all: Bloody Sunday on Jan. 30, 1972, when British troops killed 14 citizens.

The murals, created by brothers Tom and William Kelly and Kevin Hasson, began appearing in 1993 and resemble ancient Celtic crosses incised with pictorial narratives—educational, mournful, proud, indignant. As we walked the trail with heavy hearts, William Faulkner's adage rung true: "The past isn't dead. It's not even past." The long grey slab of the city's stolid wall looming over us underscored this reality.

Belfast's divisions are even starker. We had the luck to tour with Danny Murphy, a self-described ex-IRA man who had lived all his life in the Falls Road neighborhoods through which he led us.

While he avoided discussing his IRA role, Danny repeatedly emphasized that because of what he had done, he now had a responsibility to bridge the partitions so that, as he said many times, "this doesn't happen again."

We could certainly sympathize with his pledge, but even after a quarter-century, there is still a long and barbed wall dividing Catholic Falls Road from Protestant Shankill Road, with no plans about taking it down. And there are still gates that the police close at night that cut off all the cross-streets between the two communities. Same thing as the wall: no plans to dismantle them.

And these two areas have their own corridors of murals for memory and tribulation: Bobby Sands on one side, the newly minted King Charles on the other; the IRA and the UVF (Ulster Volunteer Force); the PLO and the Red Hand.

Our brief immersion in these cities left us disconcerted and humbled by what we had learned, and we certainly had no recommendations how to solve the problems, given that we can't even exorcise the ghosts of civil rights and civil war that haunt our own country.

If Brexit rekindles these simmering tensions, that would be a tragedy for a people that we found courteous and funny and deep-souled and spirited, creators of the "water of life," uisce beatha—Irish whiskey, a great gift to the world. (And while we may be courting controversy by saying this, we prefer Jameson over Bushmills.)