This Federal-style home served as the country residence of merchant Archibald Gracie in 1799. Since 1942, it's been the residence of New York’s mayors and their families (with the exception of Michael Bloomberg, who preferred his own plush Upper East Side apartment). The house has been added to and renovated over the years. To visit, you’ll have to reserve a spot online for one of the hour-long house tours held one day a week (less frequently during the holiday season).

The estate's 11 acres of grounds were turned into the pleasant, riverside Carl Schurz Park. It's popular with local joggers and dog owners, and its lovely promenade – which offers panoramic views of the East River, several islands and the Triborough Bridge – is one of the Upper East Side's hidden gems.