As architects increasingly leverage the sun to light, heat, and power their designs, understanding the interactions between the sun and the built environment is critical. Increased shadowing from neighboring buildings can render day-lighting or solar energy harvesting systems useless. Uncontrolled reflections from the building envelope can cause glare, reducing a motorist’s ability to see; and multiple converging reflections have even been known to cause property damage and personal injury. This lecture presents a series of case studies demonstrating the diverse ways the sun interacts with the built environment, and how designers can predict and understand these interactions to create buildings that take full advantage of the sun without adversely impacting their neighbors. The presentation will place particular emphasis on rule-of-thumb techniques which can avoid solar related problems and also on the strengths and weakness in various approaches to predict solar effects in an urban context.