If you have read the book Angels and Demons (Dan Brown), you probably already know about ambigrams. If not, here is a little info on what they are.
Ambigram n., – a word or words that can be read in more than one way or from more than a single vantage point. (from the Latin: ambi=both + gram=letter)
The classic ambigram is a 180-degree symmetric rotation, which means it reads the same upside down and right side up. For instance, a naturally occurring ambigram (more will be demonstrated later) is the word “MOW,” which, when turned upside down, still says “mow”. The word “mom” however, says a different word, “wow” when rotated. The true art of creating ambigrams lies in going beyond these natural ambigrams and turning any given word or words, regardless of their natural symmetry, into words that can be read in more than one way.
John Langon is the designer of these amazing designs. After reading Angels and Demons, I developed a huge interest in ambigrams and even developed some of my own. (With the help of my friend Dragan).
Check out his official website here to view many more examples, and some other amazing designs.