The Mi’ihen Highroad is a large connected roadway named after Lord Mi’ihen. These areas include the Highroad North, Highroad South and the Oldroad (among others).
The Mi’ihen Highroad is such a large area that the walkthrough and strategy guide section is broken up in to two distinct areas. Use either of the links below for more information:
10) Mi’ihen Highroad - South/Central
The first half of the Mi’ihen Highroad where you first run in to Belgemine.
11) Mi’ihen Highroad - Agency/Newroad
Arriving at Rin’s Travel Agency, defeating the Chocobo Eater and continuing along the Newroad and Oldroad to the Mushroom Rock gate.
You should make sure to pick up the 
Jecht Sphere and the Mars Crest when you pass through this area.
Note that you can opt to travel through this area on the back of a Chocobo (and can do so for free if you defeat the Chocobo Eater). Chcoobos can help you travel through this area much faster and riding one is required in order to reach some of the secret items in this area.
