Travel Time and Road Cost
How duration is calculated, how mount and alliance stables reduce it, and how gold cost is set.
Related in Travel: World Map and Travel | Travel Time and Road Cost | Travel Restrictions | Enemy Territory Risk
Travel duration is based on map distance between your current city and destination city. Even the shortest route takes at least 1 minute.
Mount level reduces travel time. Alliance stable level reduces it further. These effects stack.
Road cost is based on final duration after reductions, with a minimum of 1 gold.
If you do not have enough gold, travel fails and location does not change. On success, travel cooldown is set to route duration.