The Doctor's create a message visible from space with two cans of white paint. This is impossible. It is also right beside the Great Wall of China, playing with the popular but erroneous belief that the Wall is the only man-made structure visible from orbit. Since many stories in the Whoniverse are predicated around myths and legends turning out to be true, this bit of whimsy is justifiable.
As soon as Yaz and Dan fall into the sealed Mexican pyramid there appears to be an already lit candle.