Recently, I had a dream where I was exploring some northern swamps (like in Lapland, that kind of terrain), but it was implied that it was a fantasy setting. I found a wooden hut, went inside, searched around, saw a hatch in the roof, opened it... and found myself among sandy dunes. The feeling of the unexpectedly opened portal was powerful; it made me want to implement something similar in some game (too bad I'll never do it).
There was a residential area of some southerners nearby, and I went to a bar, and the locals were even speaking English, which made sense because if you looked at the bar, there was another European sitting there, so it was obviously a tourist spot.
In general, as often happens, it wasn't anything special, but on a purely emotional level, I liked the transition between the locations.