Personally, I'd have to say the most interesting places I've been are Thailand and Albania. SE Asia and Eastern Europe/the Balkans are super interesting regions.
Bangkok to me is such an insane experience if you dive into the seedy underbelly of it all - the prostitutes, the drugs, the corrupt police, the start-up scene, trannies, ping pong shows, etc... then you add in the actual politics of the country and it's mind boggling. All that combined with the tropical weather, beaches, and resorts where a lot of people stay and see none of it. You could also go somewhere like Chiang Mia which is completely different. That's just Thailand though, there's still all the other countries in the region as well.
Eastern Europe is heartwarming. People still have this idea that it's dangerous but the women are beautiful, people insanely trusting as well as caring, and all the history dates back along with being recent. I lived in Poland for a while then Serbia for a bit. Albania is the place to go if you're searching for "that" feeling though. The highways are dirt roads, prices super cheap for everything, and wandering around feels like a time warp. Public transportation doesn't exist so people have literally taken it upon themselves to show up to some petrol station everyday in an Astro van and charge everyone 2 or 3 bucks to load in and go to whatever city.
Now, as far as most interesting experience goes, I was kidnapped by the police in Mexico once. They pulled me away from my table for one as I was enjoying some tacos and a Margarita to frisk me. When they pulled out my pocket knife they told me pocket knifes were illegal in Mexico and threw the cuffs on me. These guys fucked with me for a while, stopped for drinks at a bar I'd been to before, then fake arrested and threw one of their friends they just shared a beer with in the back seat with me. I asked him why he was back there and he said "pocket knife" in a super crazy accent then I asked him why he didn't have cuffs on and he gave me the "ssssshhhh" sign like "don't tell them, they forgot to put them on me" haha. I started pleading and saying things like I was still a virgin, I only came down to buy cigarettes because I wasn't old enough to get them in the states, that I'd never been in a serious relationship, and basically anything else they might believe and would make them sympathize.
Dude eventually stops in this seedy alley, tells me whatever deal we make is between him and I so to stop saying anything in the car. I say take whatever you want know then and let me go. He keeps my garage door opener, the pocket knife, and my 50 bucks. I still had my credit cards so on the way back I bought churros and the carton of Lucky Strikes I went there for. Best goddamn cigarettes I've ever smoked, best food I've ever eaten.