The entry problems are not over after booking, however.

Right after I arrived at the N’Djamena airport, a uniformed officer rubbed his thumb and fingers together as I approached and said, “Money, money, money.” He asked for a bribe of $50 to let me leave the airport.

I told him, in my most forceful French, that I had already paid for my visa.

He looked unimpressed: “Money, money, money.”

I lied and told him that the Chadian ambassador to the United States had assured me that I did not have to pay more money to enter Chad.

He looked at me as if I were a simpleton: “Money. Money.”

I asked him to show me the regulation that required me to pay.

He looked at me as if I were a troublemaker.

I told him I would pay him only if he gave me a signed receipt.

He choked with laughter and shared the joke with two of his colleagues, who were waiting for their cut.

As the end of both his shift and my patience approached, the price of the bribe dropped to $15.

I had only a twenty, which I gave him, and asked for change. For this I got the biggest laugh of the day and a wave to get the hell out.

Nauru was, for me, from 2001 to 2007, impossible to get a visa to.

From the late 1960s through the early ’70s, the denizens of this tiny Pacific island were the wealthiest people on the planet per capita, due to the dense and valuable guano deposits left on the island by fish-eating seabirds over a period of eons. The last of these rich phosphate resources were depleted by 2006, and the suddenly impoverished Nauruans were compelled to make a living in other ways. First the country became a tax haven and alleged money-laundering hub for Russian criminals. Then it established internment camps for refugees as part of “the Pacific Solution” to prevent the refugees from reaching or remaining in Australia, and effectively closed its borders to all visa-seekers not approved by the Australian High Commissioner to prevent foreigners from monitoring the migrants’ conditions.

Nauru relaxed these restrictions with the formal end of the Pacific Solution in 2008. And though the country remains a dumping ground for many refuge-seekers, it is now focused on legitimate enterprises, including tourism, making it far easier to get a visa—the island’s airline arranged mine, and I finally visited in 2011. But unless you are on a crazy quest to visit every country, you might want to skip this uninviting strip-mined mess of a speck of limestone.

Russia wouldn’t have made this list but for my fourth visit there in 2010, when I discovered the liability of being an American seeking to enter Putin’s land: While most of the rest of the world’s peoples can apply for a visa to Russia using a simple single-page form of 21 questions, U.S. citizens must use an arduous “new form implemented on the basis of reciprocity” that has 41 often-intrusive questions. These include: itinerary details; the name of the person or organization paying for the trip; the names of every country the applicant has visited in the past 10 years (99 for me); the applicant’s current and two previous places of work; every educational institution the applicant has attended; all the professional, civil, and charity organizations of which the applicant is a member or with which he has “cooperated”; the names of all the applicant’s relatives in Russia; the details of any training in firearms, explosives, nuclear weapons, and “biological and chemical substances” (which arguably would include everything from acidophilus yogurt to Drano); and details of the applicant’s military service, including rank and occupation.