how do you disallow city building?

[Good Sauce]

specifically, I'm making a map and I want to prevent the AI and human from builing on desert tiles. idealy I would do this in the WBS itself, but I suspect it must be done in the XML. I looked around a bit to see if it jumped out at me but could find nothing. any help would be great.

 

[zyphyr]

In Civ4TerrainInfos.xml :

The entries that control possible city placement on a terrain type:
<bFound>
<bFoundCoast>
<bFoundFreshWater>

They are boolean values. Set them to 0 or 1.
Found : 1 = Can always build on that terrain. 0 = Can't unless one of the other two are a 1.
FoundCoast : 1 = Can build a city there if it is a coastal tile. 0 = Coast doesn't enable cities
FoundFreshWater : 1 = Can build a city there is it is adjacent to a lake or river. 0 = Fresh water doesn't enable cities