New York City
What are some of the best spas in New England? No set budget, just want something really nice.
Mentioned in this answer:
Consider heading to Cape Cod, even in the fall it has great charm and many of the shops and restaurants are still open. A great spa can be found at Chatham Bars Inn. The inn is already fabulous but I've taken girls' weekends there just for the spa. If you visit during the warmer months, it has a private, adult-only pool and anyone who receives a treatment can enjoy that pool all day and even receive room service for food and drink. Love it there!