The Cross Bucks Way is a 24-mile long path across Buckinghamshire, from Stratton Audley in Oxfordshire to the boundary with Bedfordshire at Linslade.

Closely following the ancient trade route from Wendover to Chesham, this linear walk through classic Chiltern countryside, links The Ridgeway with the Chess Valley Walk.

https://www.chilternsaonb.org/ccbmaps/224/137/chiltern-link.html

For leaflet: https://ldwa.org.uk/ldp/members/show_path.php?path_name=Chiltern+Link

A famous alpine crossing in central Europe. Traversing three countries it connects Oberstdorf in the southernmost region of Germany with Meran, a beautiful city in south tyrol with mediterranean flair.
 

This is a pretty straightforward route that traverses a National Park (albeit a tiny one) and is a fun, very runnable 50k distance that has been done a number of times though doesn't seem to be popular. We didn't see a single person on the entirety of the Under the Rim Trail, which the park describes as unmaintained. There's certainly some blowdown in Agua Canyon (through an old burn) and a handful of washes to cross but they're easy to navigate.