How about Iceland? If you're into hiking and history Iceland has both in spades, though it is not the kind of regal, storied history, that Europe has, it is fascinating, bloody, full of myth and legend, and very unique.

There is nearly endless hiking to some breathtaking locations. Friendly locals and everyone speaks English and Icelandic so you get exposure to a new language without going crazy trying to communicate. (though that may be half the fun to some people).

Tons of art in Iceland, but again not famous like the Louvre or Prado. Really quite an amazing place that isn't completely beat up by tourists and overrun by hordes, especially when compared to Rome, Paris, Barcelona, etc.

Cheap flights from the states. Not very long - 4, 5, 6 hours depending on where from.