The cathedral in Puebla, Mexico, by night. Thanks to a bit of administrative immigration grief in Oaxaca, we only got to spend half a day in Puebla but it looked nice and I did eat an enchillada in chocolate mole sauce. The sauce is called mole, it doesn´t have any actual moles in it, as far as I know.
As for the immigration authorities, if you´re ever on holiday in Mexico and are keen to get your kids off your hands for a few hours of Treasure Hunt style fun, then my tip is to neglect to obtain tourist cards for them at the US/Mexico land border. This will lead to them being asked to perform a series of apparently arbitrary tasks - buying lots of forms, photocopying every page of their passports, printing out their bank balance, paying money into a bank and getting a stamp on six different forms to say you´ve done it, finding bus tickets - both American and Mexican - to prove when they crossed the border, filling in some more forms, marvelling as the official in front of them pulls a typewriter out of the dustbin of history and completes his notes, being very polite, digging out their best schoolboy Spanglish and finally leaving exhausted and grateful after three hours.