Theres also this place https://en.wikipedia.org/wiki/Hans_Island which is disputed by Canada and Denmark. Apparently the Danes leave a bottle of schnapps for the Canadians and the Canadians leave a bottle of Canadian Club and a note saying welcome to Canada.
The border is defined as a straight line, but was surveyed as a series of slightly wobbly series of lines. They put up thousands of stone pillars, cut out a strip of trees along the border, and it became official.
IIRC there's also some stuff about a disputed island
I once visited Port Roberts just to see the border crossing. I drove in from the Canadian side, parked my car, and walked across the border into the U.S. without being challenged. No one asked for my passport. As far as I could tell, no one even noticed that I had crossed the border. But when I tried to walk back into Canada the Canadians gave me a pretty hard time and almost didn't let me back in. It was an interesting experience.
Newark is completely surrounded by Fremont (California) and has over 40,000 residents and is over 13 square miles in area, so if it's not the largest, it's at least near the top.
If we discount natural borders like the Pacific Ocean, Santa Monica borders only Los Angeles and has twice as many residents.
Los Angeles has very strange borders. West Hollywood and Beverly Hills are independent enclaves, and it has an odd tendril stretching down to Long Beach. I remember being delighted when Google Maps started outlining city borders - I had always wondered exactly what LA's looked like.
Another fun one is San Diego, which does indeed touch Mexico, but to get from downtown to the border and stay within city limits you'll have to get on a boat and stay within a narrow band of water stretching down the bay to San Ysidro.
Until this past year, the India/Bangladesh border was similar - there was even a triple-deep enclave (india inside bangladesh inside india inside bangladesh... I think...). They just recently did a land swap to make the border more sane, and also easier on the inhabitants, who didn't have freedom of movement between the parts.
Some houses in the town of Baarle-Hertog/Baarle-Nassau are divided between the two countries. At one time, according to Dutch laws restaurants had to close earlier. For some restaurants on the border this simply meant that the customers had to move to a table on the Belgian side.
The border goes through some houses as well, and the country you're in is deemed as which side of the border your front door is on. Apparently there has been a house or two that moved their front door across the border, in order to benefit from lower taxes or somesuch.
Our frontiers are sometimes a bit fuzzy to say the last [0] and there is also this place [1] where you can literally be in 3 countries at the same times
Not necessarily - If you have a body of water on the top and the bottom, and two different countries on each side, then there's no spot you can be in 3 countries at once. See: America
Someone also tried to tell me Norwood, Ohio is the largest city within a city (an enclave city), but I can't find a source on that anywhere.