The Alpine Garden, the other formal space planned by the Olmsted Brothers, is located on the ridge along the park's eastern side, to the east of the Cloisters. It contains a stone stair and a grotto. Originally planted with alpine plants, the garden later became overgrown before being restored in 2009. The garden incorporates numerous rocks, which according to NYC Parks' website " the outcroppings of metamorphic Manhattan schist". The rocks used in the garden include quartz, feldspar, mica, and garnet; some of the stone comes from excavations during the park's and subway's construction.