Another classic of the genre. G2O began life as Giuliano Spa for Beauty & Wellness way back in 1994, then went through several iterations before landing at its current, incomparable space. Housed inside a historic brownstone, G2O is the place for a modern daylong spa experience. For starters, there’s a fireplace lounge and experience room that can be filled with herbal-infused steam, as well as a salt cave and floating pod. But the cutting-edge treatments here are G20’s signature, like LED light therapy, hyperpigmentation facials, detoxifyng herbal wraps and reflexology. There’s even a separate hair salon to tend to your highlighting and Keratin needs.