Heartquest:
I was checking out this photo and realized some shadows were definitely "hard" made. They are in the 4 yellow circles. That highest one started out as a "maybe" until I lightned up the shadows big time and out popped what might be a bull's head, facing to the right. There's a speck of something giving it an eye. THEN, that lower circle on the left stayed a black cat facing to the right, and there's a small, full-bodied black cat just to the right that's ALSO facing to the right. LOL That lowest circle on the lower right could be almost anything, but it's being shielde by too many weeds.
Now for the two BIGGIES. There's a large profile of a lion's head, facing to the right, just above the heart. I've outlined it's face with a yellow line, slightly offset so as not to cover any detail on the rock itself. The SECOND biggie is that square-cut recess to the right of the heart. I've outlined it with a yellow rectangle. When I lightened up the shadows, that square cut just jumped out. I'm thinking that is the "bait chamber" for that death rock. The way I'm seeing that heart, when it's tripped, the large rock on the righ would hang up the heart's right lobe and cause it to swing it's point to the right, thus crushing the guest of honor who's trying to get into the square hole. That smallish stone on the lower left of the heart looks like it's job would be to stop the heart's slide and lock it into place covering that square opening and either pinning the guest to the big rock OR sealing him inside the bait chamber. You did say that the heart is about 8 feet tall. Pretty good fly trap. LOL
Oh, and that heart-stopping stone has a right angle chizeled on it's left side.......outlined in yellow.