Yep, it’s all just an art installation, inspired by artist Joseph Beuys as an extension of his “7000 Oaks” project. Over the course of five years beginning in 1982, Beuys planted 7,000 trees in the city of Kassel, Germany, each with an accompanying basalt stone column (intended to illustrate the opposing characteristics and yet harmonious co-existence of tree and rock, apparently). After his death, the concept was brought to West 22nd Street.

Scouting NY: The Mysterious Stonehenge on West 22nd Street

(Thanks James K!)