OK. I gave away the answer. The (25 mile, 3-day) Routeburn Track "Great Walk" in New Zealand is my favorite trail of all time. It has a lot of competition, but mile-for mile, no other trail that I have "tramped" has beat it. And I've had the privilege of walking it twice, once with Kathy on a guided tour, and once as an "Independent Tramper". In total, I have been to New Zealand four times, and Kathy has been there twice.
New Zealand has the best "backcountry hut" system in the world, and this makes many of their multi-day backpacking tramps much more easy -- no need to pack a tent, and a clean, dry roof over your head at the end of the day. Kathy and I have been in the backcountry in New Zealand on days that it rained 8" in near-freezing temperatures, and believe me, a hut at the end of the day was a blessing.
What makes the Routeburn so great? For one, great views:
Also, fantastic trees and colors:
And, exquisitely beautiful valleys, among other things:
If you can afford the airfare, put New Zealand on your bucket list and go there. You will thank me later.