“What did they do to you?” he asked when he saw me reappear that evening. I told him I had had a bad meal, taken a walk, seen a museum and generally gotten an unedited glimpse of the grim and threadbare life of East Germany.

Not all warnings are frivolous or self-serving. In 1973, I was warned not to go to Khmer Rouge-controlled Cambodia, and that was advice I heeded. It seemed to me foolhardy to go to a country in a state of anarchy. I wouldn’t go to present-day Somalia or Afghanistan either. Nor is Pakistan very tempting.

I traveled to Vietnam that same year, just after the majority of American troops withdrew and about 18 months before the fall of Saigon. The country — though a government was intact — was adrift in a fatalistic limbo of whispers and guerrilla attacks. It was less a war zone than a slowly imploding region on the verge of surrender. My clearest memory was of the shattered Citadel and the muddy streets and the stinking foreshore of the Pearl River in Hue, up the coast, the terminus of the railway line. Now and then tracer fire, terror-struck people, a collapsed economy, rundown hotels and low spirits.

Thirty-three years later I returned to Vietnam on my “Ghost Train to the Eastern Star” journey, which was a revisiting of my “Great Railway Bazaar.” I went back to the royal city of Hue, and saw that there can be life, even happiness, after war and, almost unimaginably, there can be forgiveness. Had I not seen the hellhole of Hue in wartime I would never had understood its achievement in a time of peace. Seven million tons of bombs had not destroyed Vietnam; they had if anything unified it. And Hanoi, which had suffered severe aerial bombardment over the many years of the war, looked to me wondrous in its postwar prosperity, with boulevards and villas, ponds and pagodas — as glorious as it had been when it had been the capital of Indochina. It is certainly one of the most successful, and loveliest, architectural restorations of any city in the world.

Just a few years ago Sri Lanka emerged from a civil war, but even as the Tamil north was embattled and fighting a rear-guard action, there were tourists sunning themselves on the southern coast and touring the Buddhist stupas in Kandy. Now the war is over, and Sri Lanka can claim to be peaceful, except for the crowing of its government over the vanquishing of the Tamils. Tourists have returned in even greater numbers for the serenity and the small population. (Amazingly enough, almost the same number of people live in the Indian city of greater Mumbai than occupy the whole of the Democratic Socialist Republic of Sri Lanka.)

At one point Sri Lanka was on the Could Be Your Last Trip list of the traveler Robert Young Pelton. He has made a career of clucking about hazards, descriptions of which fill his books, notably “The World’s Most Dangerous Places.” On the one occasion when we met in the late 1990s — on a TV show taped in New Jersey — he came across as a genial if torpid Canadian, except when he was talking about the horrors of Sri Lanka, the Philippines and Colombia. I had made pleasurable trips to all three, I said. And I was compelled to point out to him that we were on the outskirts of Newark, at the time advertised by its own newspaper, The Star-Ledger, as New Jersey’s homicide capital.

The earth is often perceived as a foolproof Google map — not very large, easily accessible and knowable by any finger-drumming geek with a computer. In some respects this is true. Distance is no longer a problem. You can nip over to Hong Kong or spend a weekend in Dubai, or Rio. But as some countries open up, others shut down. And some countries have yet to earn their place on the traveler’s map, such as Turkmenistan and Sudan. But I’ve been to both not long ago — one of very few sightseers. And along with oppression and human rights violations, I found hospitality, marvels and a sense of discovery.

In my own “Tao of Travel,” the fact that a place is out of fashion, forgotten or not yet on the map doesn’t make it less interesting, just more itself, and any visit perhaps more of a challenge. But travel maps have always been provisional and penciled in, continually updated. The map of the possible world being redrawn right now — parts of it in tragic and unsettling ways — might soon mean new opportunities for the traveler who dares to try it. Travel, especially of the old laborious kind, has never seemed to me of greater importance, more essential, more enlightening.