What is the Kaaba?

I’m sure you’ve seen pictures of devout Muslims walking around a huge rectangular object in the heart of Mecca. But what is it and why is it so significant in Islam?
It is called the Kaaba. Inside this enormous cube, the holiest object is the black stone. Nobody is sure what it is but it could be a meteorite. Equally shrouded in history is why the object is so venerated, especially since it precedes the foundation of Islam.
You’ll find more explanation of the Kaaba and discussion of its meaning here.
Maybe Muslim readers would like to share what the Kaaba means to them.