Complex sentence: In 1968, in Philadelphia's Rittenhouse Square, McWilliams performed his composition "Sky Kiss", in which he attempted to levitate while hanging from a bunch of helium-filled balloons.
Split into simpler sentences: In 1968, McWilliams performed his composition "Sky Kiss" in Philadelphia's Rittenhouse Square. In that piece, he attempted to levitate while hanging from a bunch of helium-filled balloons.