"A gorgeous 281-acre green space within Boston, Arnold Arboretum of Harvard University is the oldest public arboretum in North America (c. 1872) and the highlight of Frederick Law Olmsted's famed Emerald Necklace series of green space in the city. Prolific biking and walking trails zigzag past more than 16,000 accessioned plants, many meticulously marked with signs. The natural splendor is a feast for the eyes, which are able to spot the sheer diversity of trees and plants at every turn. QR-coded signs and the arboretum’s easy-to-use Expeditions app make it possible to dig deep into the environment." - Paul Rubio, Todd Plummer