Sri Lanka is pretty dang cool. The UA is really strong but kind of...incites greediness in looking for places to really make use of it to its fullest, since it's only okay on just little spots of rivers, so you're on a bit of a quest for a promised land of lots of river valleys, which end up super strong since normally they have big production problems. And the UU helps support it since eventually you'll run into resistance, and they excel at conquering the exact places you will want to settle. The second part of the UA and the UB are a little just there but they do evoke particular decisions to focus on faith buildings in your religion (assuming the UB counts those and not just Shrine/Temple/Monastery).
I had a particularly interesting game where barbarians were very rampant and I was kinda isolated by a bunch and the borders of a city-state, but taking the plunge to explore there with a settler led me indeed to what were pretty much the Tigris and Euphrates with Lake Victoria right there and I was all over that. ...But Germany was right there and took one of my prime spots, which signalled a push to start the war machine to get my UUs in gear, and it was a really interesting game since I was in a decently strong start but with definite challenges to overcome, as any good expansion needed to be functionally overseas and right in the face of somewhat militaristic powers.
...then the game crashed but well. It was cool! Kinda wish the decisions worked, that was a bit of a bummer, but I had fun nonetheless.