B&B Italia Outdoor’s Canasta sofa, by Patricia Urquiola, shares a shady patch in the ground-floor Carnegie Hill garden with three ginkgo biloba trees, an existing fountain with an Italian marble spout designed by Thomas Woltz, and bluestone pavers. The terrace is filled with woodland greenery: Leucothoe, ostrich ferns, and lady ferns.  Small footprint from Nelson Byrd Woltz Harnesses the Natural Elements