While the mathjocks among you might recognize this structure as a (fractal) Sierpinski Tetrahedron, note that it was constructed with baseball bats and softballs [ht JH]:
JH adds, "the photo comes from a book in honor of the 50th anniversary of the Insitute of Mathematics at the Royal Society, copyright Gwen Fisher."[cf this site]
It seems appropriate to post this now, as I prepare to head off to Labatt Memorial Park in London to watch game 7 of the IBL semi-finals, between the London Majors and the Kitchener Panthers.
Update: The London Majors won the game and now move on to the finals for the league championship.