The best place is the search button in the forum In fact this question has already been asked quite a number of times, you should find a good list of beautifull places, even for the full default game
KGEV (my home airport) Nice route in Alaska - 5Z5 to PASW in a twin prop. have to fly over Mt. McKinney The takeoff and landing while not hard does require some effort.
try the lovely carribean islands , and mainly St Marteen and San Juan, then up to Florida. Notice the sunsets in Africa look the best I have....check out the mountainous regions of the world , I just got back from South America, and I can tell you taking off at over 9000" in a piston can be hard work on full tanks ! in fact the Baron would not even start without the fuel pump on hi and the throttle half open !
whant a challenge? the hardest thing I have done is land into Queenstown , New Zealand (though a mountain pass approach) , in a 747 at night or poor weather ! In fact , during the day looks best , but done blind IFR is a real buzz with the online ATC 'watching' you !
Alaska looks cool also. ....should I go on ? avoid Melbourne though , they're all hippies down there....