In Augusta, Maine there is a Thai restaurant just outside the restricted area of the airport/ National Guard base. The fence between the restaurant and airfield has some very dire warnings posted on it about feeding the birds. However, the food there is very good and reasonably priced. If I am working in that area I tend to go there to eat.
This might be pushing the definitions a bit, but when a friend was in University Hospital in San Diego, and his friends and family were on what might have been a death watch (he survived!) we ate in the hospital cafeteria quite often…and were comforted by some darn good eats.
If it weren’t both bizarre and inconvenient, I’d drop in, even now, for a meal.
I had a friend who lived in Buenos Aires for a while, and of all the places to eat in that Latin American city she would make it a point to take everyone who came to visit to the cafe at the Swedish embassy (the meatballs were good!)
One of the best Chinese restaurants I’ve been to was in the middle of nowhere, over a mile off the freeway, somewhere in (West?) Virginia I think. Our previous meal at an “Italian” restaurant in the countryside had been rather awful, and we were not expecting much, so perhaps just that it was as good as any other Chinese food made it seem better.
The best Indian food I’ve had outside of India was at a tiny hole-in-the-wall restaurant in Montpellier, France. You had to walk past the fancy cafes lining the big plaza in front of the opera house and go into narrow streets and alleys of the medieval heart of the city. The Indian folks I was with had discovered it first, so I knew it had to be good. The place had all of two tables - one inside and one outside. It was summer so we ate outside. The food was quite authentic and indeed very, very good.
Pinel Island, a tiny bit of sand off the coast of St Martin has an incredible restaurant. The island is a nature preserve, however, and lacks electricity, running water, etc. The restaurant workers haul boatloads of coolers each day and cook using bottled gas. Fishermen stop to offer their catch. There is a water taxi to Pinel, but we often rent kayaks for the day.
The restaurant in the US Embassy in Copenhagen used to be a 4-star joint that even had a wine list. Perhaps it still is.
One of the best Italian restaurants I’ve eaten in was a place in Kampala, Uganda. It was owned and cheffed by an American expat and his British wife. The best Indian food I’ve ever had was also in Kampala. That’s not really surprising, considering all the Indian expats who live there.
I’ve posted before that the best burger I’ve eaten (in the millions I’ve had) was in the tiny no-horse town of Spencer, Idaho off of I-15.
The Double Musky Inn. Girdwood, Alaska. A great place for dinner after a day of skiing on Alyeska. This is before the huge resort was built. The recipes used to be free and every year I try my inept hands at the salmon appetizer.
Coconut Salmon
Salmon chunks dipped in beer batter then rolled in coconut, deep fried served with a sweet and sour plum sauce.
This was a couple decades old, but the story is the “best” restaurant in San Jose CA was at the IBM site cafeteria. (Maybe not the best, but darn good.) Supposedly the word got around and they started getting tour buses stopping and unloading their passengers for lunch until management got word of what was going on.
Sea World in San Antonio, TX has some surprisingly good brisket.
I found a wonderful French restaurant in a strip mall in Lubbock, TX. So strange, but so, so good. I found a delightful bistro in the small community of La Junta, CO. I found a very good Mexican restaurant on the island of Guam. All of these were a number of years ago, but they were all definitely memorable. I also remember the wonderful French pastries in the jungle outside of Vientiane, Laos.
The best steakhouse I’ve been to is in Greenville, MS. I’ve eaten at some of the best steakhouses in the world. Better than any place in NYC, KC, Chicago, Dallas, Houston, LA, Sao Paulo, Rio, Buenos Aires, or Mexico City.
How about the goodest place I’ve ever found a strange restaurant? 
I was surprised that there’s a large cafeteria inside the Ikea furniture store.
And even more surprised that it offers a good, satisfying lunch (swedish meat balls, of course, but also salmon and lots of side dishes.)
The best Thai place I’ve ever been (and reportedly the best in the country) is the Lotus of Siam, which is in an incredibly seedy strip mall well off the main drag in Las Vegas.
The Indian Restaurant at this truck stop on I-70 (Spiceland, IN) is authentic, spicy, and really good.
It’s called A Taste of India.
And if you find yourself on the island of Saba, there’s a Chinese restaurant called “Saba Chinese Restaurant” that is well worth a visit.
How did you happen to find yourself on Saba?
Where we stay when vacationing in St Martin, we can see Saba on a very clear day. It’s pretty cool; you can define “clear day” by being able to see this giant volcanic island, anything but crystal clarity and there is nothing there.
Heh, I’ve been to Saba. Nice place for a very relaxed sort of vacation.
Flying into the Saba airport was … an experience. It’s the smallest possible landing strip, so small you would think no airplane could possibly land on it!
It’s where the plane landed. 
Vacation.
How are you dining inside embassies?
The local US embassy won’t even let citizens inside without an appointment.