Bug with 256x256 mapmaking?

[Xentropy]

I saw mention of a bug or bugs with maps the maximum size in a few threads, but no details. I'd like to know what these bugs are, and what the maximum size is which can be safely made if 256x256 isn't safe.

[Badtz Maru]

Well, for one thing you are going to hit the 512 city limit eventually, which can lead to really long turns as AI settlers will keep trying to build a city when they can't.

[Xentropy]

Originally posted by Badtz Maru
Well, for one thing you are going to hit the 512 city limit eventually, which can lead to really long turns as AI settlers will keep trying to build a city when they can't.

I see. Though if that's a real problem, the unfortunate conclusion I come to is that 180x180 or so is really the largest that should be created. At two-thirds water coverage (earth norm) that's 10800 land tiles or, assuming a perfect city placement pattern with no overlap or missed tiles (and some overlap, some missed tiles are going to cancel each other out so this isn't too inaccurate an estimate), room for 514 cities. I was really hoping to go larger than "Firaxis huge", in order to make an Earth map that's even more realistic than 180x180 can attain.

[Xentropy]

Wait!

I just noticed via the editor that only [even, even] and [odd, odd] coordinates exist the way the maps are made! This means even in a 256x256 map, as long as water coverage is at least 70%, 512 cities is plenty of slots to never be reached!

In my last post, I made the faulty assumption that a 256x256 map would have 65536 squares, but due to the way the grid system works, there are actually 256x256 / 2 + 128 squares, or 32896. At 70% water coverage, that gives you 32896 * 0.3 = 9868.8 land squares. At 21 squares per city, that's 470 cities.

Granted that's 470 landlocked cities. Coastal cities will utilize an average of 10.5 land tiles and the rest water. Still, assuming beefy enough continents rather than an archipelago, that 42 city buffer should be enough.

So, other than the 512 city limit, are there any bugs with 256x256 maps I should know about before I continue?