All squares with more than 7 are special squares, and you cannot settle on or move to special squares. You could settle nearby and claim sovereignty.
Just in case, some special squares have a normal 7 or less distribution of resources. There's a list of tile types somewhere, dolmen, ancient forest, and others are always special squares.
Try to find a normal 7 food square with at least a 30% food bonus in five nearby squares. It doesn't matter how, 32=12+4*5 and 31=3*7+2*5 are okay, 33=4*7+5 and 34=10+4*6 are better. You could then use the food bonus of five nearby squares to get a huge town, and the remaining sovereignty structures can accelerate the training of new troops.
Don't nail me with 30% on 5 squares, maybe it should be 40% on 7 squares, or more, if you can't arrange a 16% geomancy food spell.