UPDATE:  SOLVED by Nick

Yay, another Saturday.  Are you ready to riddle?  Got those brain cells revved-up and ready?  Okay, today’s subject is an object, and here are the clues:

This is a single object.

It was known to ancient man.

It features a large, well-known optical illusion.

It’s also home to something very large.

If that wasn’t enough, it boasts an impressive pareidolia.

This object is very well represented in literature.

This has been an object of intense scientific scrutiny.

Pieces of this object have recently caused considerable controversy.

There… clear as mud.  Really, it’s an easy riddle, and one of the last easy ones left.  They’ll get progressively harder after this, leading up to the bonus riddle.  Do you think you have the answer?  You know where to find me.

Spidey-smiley - Lurking