lockstep
Prince
Or just mod Buildings.xml to eliminate the line:
<ProhibitedCityTerrain>TERRAIN_PLAINS</ProhibitedCityTerrain>
That's essentially what my tiny mods does:
Code:
<GameData>
<Buildings>
<Update>
<Where Type="BUILDING_STONE_WORKS"/>
<Set ProhibitedCityTerrain="NULL"/>
</Update>
</Buildings>
</GameData>