Exploration

Exploration in Civilisation took a lot of pushing units around the map, which is not fun and, given the units were full-sized military units, not realistic (based on a Legion a Civilisation unit would be 5,000 men, by contrast Dr Livingstone's expedition to find the source of the Nile was a couple of hundred men).

In reality, much knowledge of the world would be picked up from travellers and merchants. So each civilisation would gradually accrue knowledge about the world over time, with the rate dependent on the level of trade and place in the trade route.

In addition, exploration expeditions would be controlled not by pushing units around the map (although this could be done) but by a commissioning dialogue. Expeditions would cost resource and would return map information, prestige (first circumnavigation, finding the source of a particular river, first to top of highest mountain, first to poles, etc) and territorial claims. Obviously there would be some risk that the expedition would get lost and there would be no return.