I can't believe how much this captures the feeling of Big Bend. What I really like is how you've woven Severus's magic into the magic of the location and the way the muggles just absorb the idea without question. I'm sure it has to do with the towering landscape-- you just know there's magic afoot!
As for Harry, he has really grown up (though I like how Hermione still has to do his 'homework'! What is great is how he continues to grow after he arrives.
Your ending is so tantalizing! I want to know more how they settle into their relationship with each other, how and where Severus has been living, and what it all means for Harry's life back in England.