I'm so sorry, it's impossible to express the great form of this stone with photo. It isn't geometric sphere, it's philosophical sphere.
I've seen a big pothole where is the upriver district of Mississipp. Pothole was made by a piece of rock on a bedrock and strong river stream. A piece of rock had eroded away a part of bedrock in a circle with river stream. Some big hole are around 20 meters in diameter and 20 meters deep.
These hole are not only very beautiful but also a stone which had made a deep hole is extremely beautiful and impressive. It is also philosophical sphere. A stone's strong presence is just the same as a planet.
I took some photos of it, but it's also impossible to express stone's existence. It's so perfect and beautiful.

Next photo is the Sculptuer Samurai. The Sculpture Smurai has been keeping environment clean and guarding environment against deatruction. A cat face on their T-shirt is a face of stone's stray cat in Boyd park. The cat likes always clean and safety even so a stray cat longs for freedom.
These nice and improtant activities are also part of Public Art Saint Paul.