My husband, Peter, and I spend the winters in San Miguel de Allende, Mexico. The center of the town is a designated World Heritage Site, which means the facades of the buildings must remain as they were in the mid-1700s. The streets are made of round and sometimes slippery cobblestones. The doors are stout and covered with hundreds of coats of paint, and on the top of every building is a rooftop terrace where people can watch the fireworks that go off for no reason that anyone has ever been able to figure out. It is wonderful.But there is another ...