British artist Andy Goldsworthy celebrates the Presidio's landmark forest in this ongoing, organically evolving project. Goldsworthy has created four site-specific installations, all making use of trees felled as part of the Presidio's reforestation and park management efforts: Spire (2008), Wood Line (2011), Tree Fall (2013), Earth Wall (2014). Over time, the natural materials used in Spire and Wood Line will decay and return to the earth.