Among his past projects are Artpark in Lewiston, NY, where he installed a group of 72 slate-on-wood structures; Grizedale Forest Sculpture Park in Cumbria, England, where Silurian slate centered the energy of an old stone quarry; and the University of Papua New Guinea, where Del worked with students installing a teak wood tower using traditional techniques. Other site works are at the West Dade Regional Library in Miami, Florida, in Berlin, Germany, and South-Korea.
Recently, Del Geist and Patricia Leighton collaborated on Barum Stenning in Barnstable, England, commissioned by Devon County Council; and on Passage, at the US Border Station, in Roosville, Montana, commissioned by GSA Art-in-Architecture.