3xX
Xiloxoxtla (colloquial, also approved at GeoNames; the official name is Santa Isabel Xiloxoxtla),

photo CC BY-SA 4.0 Isaac Vásquez
Note: I also found a 5xO in Mexico:
5xO
Ocozocoautla de Espinosa (also known as Coita),

photo © pemozi
And now, for the next one, there's also a 5-letter town:
5xY
Ysbyty Ystwyth, Wales,

photo © The Lowland Hundred
There are some 4xZ in Poland.
















