How did I have a dream about somthing before I even knew about it?

When I was like 12 years old I had a dream I was walking by an electronic store and looked directly at a big crowd gathered around its window. In this window was old television sets showing what looked to me like a volcanic eruption on cnn. But it was no volcano, it was a pyramid that looked stair- like. Out of confusion I asked an old lady next to me in this crowd "What happened?". She told me "An explosion happened in Mexico. Now I know it sounds just like a regular dream, but what's freaking me out is I did not know these pyramids actually existed until like a year ago.(I even have a drawing here to prove it with the date. I drew a picture of it I can even picture it in my head like it was yesterday.) These pyramids are the myan pyramids. But what freaks me out the most is I just found out like a day ago those myan pyramids are in Mexico.(what that old lady in my dream told me).10 yrs ago I had this dream before I even knew about the myan controversy and theories. I'm not saying i believe in it, I just think its weird to dream about somthing I had no knowledge of and it actually exists. Does this make sense to anyone. Can someone explain this to me? How did I dream of somthing I didn't even know existed and it actually exists!