Optimal urban land reuse relies on appropriate, occasionally visionary, planning and a sound conceptual understanding of how the land will interact with engineering and thereby society. The current ecological footprint of Homo sapiens cannot be supported for long, and that of developed societies is becoming increasingly unacceptable worldwide. If we accept that you cannot successfully manage what you cannot understand, then we need to understand the land beneath our feet if we are to be judged wise stewards of it by succeeding generations.