The expansion pack to Galactic Civilizations III, Crusade, adds a new multicore job system for handling turns. This means that turns are dramatically faster late game.
When Crusade first game out, people asked for even bigger maps. So the first update (due this week) has them.
Now, I don't recommend this map size. I don't personally play it at this map size (or insane before it). But many people really love these crazy large maps.
So here's a game of AI vs. AI I'm using for testing.
Be warned: It uses 15 GIGABYTES of memory and is pushing my 10-core PC pretty hard. At this size, turn times are not going to be fast. In the map I'm playing, there are 64 players. If you figure that each player is able to move in just 1 second, that's still a minute per turn and 1 second would be really fast given the size.
With those caveats, let's take a look..