Travel times from Venice to a number of other European cities. What is interesting is the difference in time to reach a few of the destinations (e.g. 10 days to Augsburg, vs 16 to Brussels vs 20 to Nuremberg). Part of these differences are likely due to the physical geography of Europe - Even though it is a relatively compact region, it is still bisected by numerous mountain ranges and rivers:
The Europe of the Middle Ages and later was built partly on the remnants of the earlier Roman Empire, including its relict infrastructure. The northern Roman frontier, with a few exceptions, was the Rhine/Danube rivers, and the empire's roadways reflected that:
So you're sandboxing, or just moving the adventure from place to place - Does the setting have 'Roman roads' or are there gaps where moving cross-country or along goat trails is necessary? Can the PCs catch a river barge? How many bridges or ferries cross that big river through the center of the map? What are the differences in challenges or potential encounters along that longer-but-faster route, vs the shorter-but-difficult route?
Many of the fantasy or gaming narratives place the PCs in a dark ages world living in the shadow of old empires. Do the cobblestone roads of that old empire still carry traffic?