How many foreign countries have you visited in one day?

Why would anyone want to visit multiple countries in one day?  What do you learn about that place and its people in an hour?

My four countries in a day was much more pleasant - and done by bicycle!
From Lindau (Germany) through Bregenz (Austria) on to Buchs (Switzerland) and Vaduz (Liechtenstein) - a pleasant and almost entirely flat tour of just 70km. I can recommend it!

Visited two countries, France and Germany from Switzerland in one day by walking.

When I was young and newly excited to be overseas, I bought a car in what was then (1964) West Germany, met up with my flatmate, and drove back to London. We thought it was pretty cool to zip in and out of countries just to get our passports stamped - in those days before such activity became highly suspicious. One day we flicked in and out of Germany, Luxembourg, France and Belgium - at least once each! Happy days.

El_Jost wrote:

Visited two countries, France and Germany from Switzerland in one day by walking.

Classy.
I can't come close to the OP, but I did walk from Malaysia to Thailand.
We got was was described a a taxi from the border into town.
The taxi was a tad short of a London black cab and a lot more like a rusty lump of junk we didn't actually have to push, but expected to.
The south of Thailand is a world away from the capital or tourists traps; it's jungle with a surprise up every little mountain path.
We drove up what can only be described as a slightly wider than average donkey track, trees scraping the 4 wheel drive on both sides, all to get to a Buddhist monastery most people have no clue exists.
After that, we sipped coconut by the side of a hot volcanic lake.

Oh, and in a moment of madness (I have a lot of them), I jaunted from Doncaster to Gretna  green on a Honda XBR 500.
There and back in a day.
Up the A1, down the west route.

mas fred wrote:

We got was was described a a taxi from the border into town.
The taxi was a tad short of a London black cab and a lot more like a rusty lump of junk we didn't actually have to push, but expected to.

Fred, we probably should open a new thread for unusual border-crossings, but let's just see if I can sneak in this little anecdote from my old travelling days. (The full story is in my blog's Archives of March 2012, titled "A back road to Bulgaria".)

... Entering Bulgaria with Linda four months later was simplicity itself, with a visa from Istanbul. Leaving the country was rather more memorable, occurring on yet another back road. Yet again, my car was the only traffic for miles around  the only vehicle wanting to cross into Romania at this godforsaken spot, at least.

My side of the conversation went something like this, in pidgin German interspersed with occasional words from my Bulgarian-English dictionary... "It has been a pleasant stay in your beautiful country. Now please change our unspent local currency into Romanian currency. Oh, well, any currency will do. Well, if you don't have any foreign currency, never mind; we will exchange it at the Romanian post just over there [a hundred yards across a bridge]. What?! It's illegal to take Bulgarian currency out of the country? Never mind, we'll go back to the petrol pump a few miles back and spend it there. What do you mean you've already stamped us out of Bulgaria? Well, stamp us back in again, please. We would need another visa for that? And you aren't authorised to issue visas? Sheesh. Tell you what, you keep our passports and we will drive back and get the petrol. Oh dear. We can't travel in Bulgaria without a passport. So we must just give you the money, and you will give us a receipt? Hmm. I don't think so."

I demanded to speak with the Ministry of Tourism, then Foreign Affairs, then Internal Affairs, then the Prime Ministers Office; oh, and the British Embassy. Please. Pronto. The phone rang hot for the next three hours, while we sulked in the car and wondered if we might have to stay in it all night.
In the end the Romanians changed the money for us without a fuss.  It wasn't illegal for them, which was just as well, I guess.

Back in 1999, I had a 4 country experience on the day I had to travel to Bahrain for my final interview.

Left Colombo, Sri Lanka early in the morning.

Transited via Abu Dhabi, UAE en route - about 2 hours - with a change of plane and refreshing visit to the toilet

Landed in Bahrain. about 9 hours in Bahrain, few interviews, lunch, city tour and shopping.

Left Bahrain and travelled via Muscat, Oman. Transited there for about 2 hours and then I was on my way back to Colombo.

Landed in Colombo exactly 23 hours after I had initially left.

All in a day's travelling ... and I got the job!

I don't think you can count it a visit, if you haven't left the airport perimeter.