Countries inside Countries
When it comes to neighbors, most countries have several options: like North to Canada or South to Mexico. But there are countries that don't have this freedom of choice, not because they're islands but because they're trapped in another country. For example: tiny Vatican City, which fits inside of not just Italy, but also just Rome.
How Vatican City got surrounded is complicated, but not unique for there is also the Republic of San Marino, home to 30,000 citizens which Italy also completely surrounds. Italy, apparently, is a country that likes countries in its country. But trapping nations is not just Italy's thing for there's also Lesotho, in South Africa which is both the largest encircled country at 70 times Vatican City's size and the most populated with over 2,000,000 citizens.
The thing that makes these three countries' borders bizarre is that any path in or out must go through the one and only neighbor they have. But now take a look at The Gambia, which excluding that tiny ocean border, is as surrounded as any nation can get. If we amend the previous rule to every land route, now we've made a category of single-neighbored nations.
Which includes all four of these and countries like Portugal, where the only way in or out is through Spain. Who else is on this list? Well, there's Monaco which must go through France, Qatar through Saudi Arabia, Denmark through Germany, South Korea through North Korea (though South Korea might as well be an island nation for most practical travel purposes), East Timor and Papua New Guinea both through Indonesia, Brunei through Malaysia.
And there are two sets of twins: there is The Dominican Republic whose only neighbor is Haiti and Haiti, whose only neighbor is The Dominican Republic. And the second set is: Ireland through the United Kingdom and the United Kingdom through Ireland.
A side note here: While there are tons of 'British' places around the world, some of which border other nations -- these are not part of the United Kingdom. It's complicated. Though if you wanted to, you could argue that the United Kingdom technically dug a land border under the channel to the continent, presumably to be closer to France, her best friend ever.
Finally, there's one more country in this category: Canada: the largest single-neighbored nation in the world.