New York City’s Flatiron District is becoming a wellness epicenter, with startups settling in the blocks between Union and Madison squares. In between facials at Rescue Spa, classes at Exhale and lunch at abcV, type-A New Yorkers can turn to a C-suite of holistic medical and fitness experts. “It’s the best neighborhood in the world for health and wellness concepts to debut,” says Amanda Freeman, co-founder of exercise studio Stretch*d. “The mix of clientele and the density of offices and residential buildings are unparalleled.”