This document discusses designing high-performance computing (HPC) facilities for next-generation HPC systems. It notes trends towards increasing cores and threads per chip, improving power efficiency through process improvements and integration. The document presents data showing declining floor space needs per petaflop, from 171 sqm/PF in 2012 to an estimated 1.5 sqm/PF for the planned Aurora system in 2018. It also estimates the floor space and power required to build a 33 PF system with today's #1 performance would be around 50 sqm and 2.4 MW using very high density racks, or 100 sqm using 50% lower density racks.