“Spire” consists of 37 steel-armatured cypress tree trunks, felled as part of the Presidio’s re-forestation program. The structure’s core sits below ground in a metal sleeve enclosed in a massive reinforced concrete base.
The project isn’t complete yet; it is still under construction, fenced off and surrounded by bulldozers and other heavy equipment. Even at this stage, it’s an impressive site. A spire generally sits atop a building as a kind of ornament. Goldsworthy’s Spire sits on the earth, among trees both young and old. Wikipedia describes spires:
Symbolically, spires have two functions. The first is to proclaim a martial power. A spire, with its reminiscence of the spear point, gives the impression of strength. The second is to reach up toward the skies. The celestial and hopeful gesture of the spire is one reason for its association with religious buildings. A spire on a church or cathedral is not just a symbol of piety, but is often seen as a symbol of the wealth and prestige of the order, or patron who commissioned the building
Goldsworthy says that he hopes he can give this single spire some company in the near future.