This is a tricky question to answer. There are different kinds of 'beauty' and what one person sees as beautiful another may not see as beautiful. It certainly is, as the old saying goes in the eye of the beholder.
You may see a stunningly beautiful person, but if there personality doesn't match, then they are not a truly beautiful person. On the other hand you may meet a person who isn't anything special to look at, but who through their personality is a truly, beautiful person.
So to answer your question, real beauty comes from within.