PowerFrame's Travel rules are detailed and comprehensive, based around a World Map made up of 20km wide hexes. Here's a sample page, which discusses how to use the World Map in play.
Land hexes are made up of both Topography and Vegetation, which can be combined to represent almost any environment - from Arid Flat to Jungle Mountains. Some weirder combinations create specific terrain; Arid Swamp represents a salt marsh, and Frigid Swamp becomes tundra. Personally I am quite fond of Forest Mesas.
In addition to the basic Terrain and Water icons, there are other markers for settlements, fortifications, sites, ruins, caves, mines, cliffs, beaches, roads, streams, rivers, cataracts, waterfalls, and oases.
Once you have a map together, the rest of the Travel rules respond to the variable terrain as the party travels over it. While you can skip stuff that's not important to your game, you can use the full rules to play a procedural hexcrawl and explore a fantastic landscape. There are rules covering Weather, Encounters, Getting Lost, Movement, Vision, and Exposure.
- Weather is influenced by the terrain, and other factors such as season and latitude. It's based on separate sliders for Temperature, Water, and Wind.
- Encounters provide general suggestions, since it's a universal system. The terrain affects your chances of encountering either Creatures or Characters. I've tried to make sure each Encounter is more than just flavour, and the Character Encounters have hooks to help get the PCs involved.
- Getting Lost is a possibility in some terrain, with mountains and forests disorienting and misdirecting travellers. Use of the appropriate Abilities will make sure you go the way you intend, and don't just walk in circles.
- Movement uses the characters' normal Movement rate on the World Map over a 12 hour period. However, travelling too much can sap Endurance, so it's often wise to slow down a bit unless you really need to be somewhere.
- Vision is a key element when exploring new areas. As the party progresses, the GM can fill in the Players' Map with just the areas they can see. You can usually see all the adjacent hexes. Some terrain and weather obscures vision, but mountainous terrain can be seen from further away than usual.
- Exposure is a risk if the weather is particularly hot or cold. It drains Endurance, which can make travelling more difficult and eventually prove fatal.
This flexible and adaptable system is designed to help you create and explore your own worlds, whatever they might look like.