What is heaven?

Last night we were driving to the playground and somehow, Papa (Anne's father) came up. We explained that Papa is in heaven now and Mary Grace asked "What is heaven"?

This was one of those interesting moments in a parents life that you both look forward to and kinda don't look forward to. How does one explain heaven to a three year old?

I looked at Anne and she started the following explanation: You were in heaven before you were in mommy's tummy, then you were in mommy's tummy, then you were born. And someday you'll go back to heaven.

Mary Grace's response was classic: "Hmm, I've never been there".

Anne came back with: You don't remember it because you were so little, but you were there.

That seemed to satisfy her curiosity for the time being, as we quickly jumped to the new subject of releasing the squirrel that I caught (the one that was eating my tomatoes) into the park behind the playground.