Complex sentence: The previously open-sided balaconies of the atrium space are now solid walls lined with slabs of recycled slate, sand-blasted to show the major stars in the night sky and the planets in the solar system.
Split into simpler sentences: The previously open-sided balconies of the atrium space are now solid walls lined with slabs of recycled slate. These are sand-blasted to show the major stars in the night sky and the planets in the solar system.