Vanderbilt Mansion National Historic Site, located in Hyde Park, New York, is a magnificent Gilded Age estate that serves as a window into the glamorous lives of the Vanderbilt family. Here is a summary of the site, including reasons to visit, points of interest, interesting facts, and the best time to visit.

Reasons to Visit:
1. Historical Significance: The Vanderbilt Mansion, built between 1896 and 1899, was once the country home of Frederick William Vanderbilt, a prominent member of the Vanderbilt family. It offers a glimpse into the opulent lifestyle and social history of America's elite during the late 19th century.

2. Architectural Marvel: Designed by renowned architect Charles McKim in the Beaux-Arts style, the mansion is a stunning example of the period's grand architecture, featuring ornate interiors, exquisite craftsmanship, and beautiful gardens.

3. Scenic Location: Set on a sprawling 211-acre estate overlooking the Hudson River, the Vanderbilt Mansion offers breathtaking views of the river and the surrounding landscape, making it an ideal destination for nature enthusiasts.

Points of Interest:
1. The Mansion: Visitors can explore the Vanderbilt Mansion's three floors, including the grand entrance hall, opulent reception rooms, lavish bedrooms, and an impressive collection of original furnishings and decorative arts.

2. Formal Gardens: The meticulously maintained Italian gardens surrounding the mansion are a highlight, featuring terraces, fountains, marble statues, and vibrant flower beds that provide a serene and picturesque setting.

3. Visitor Center and Exhibits: The site's visitor center offers exhibits and multimedia presentations that delve into the lives of the Vanderbilt family, the Gilded Age, and the mansion's architectural significance.

Interesting Facts:
1. Historic Preservation: The Vanderbilt Mansion was one of the first historic sites to be acquired by the National Park Service, ensuring its preservation and accessibility to the public.

2. Socialite Gatherings: In its heyday, the Vanderbilt Mansion was a hub for elite social gatherings, attended by prominent figures such as Presidents Roosevelt and Wilson, as well as influential artists, writers, and politicians.

Best Time to Visit:
The Vanderbilt Mansion National Historic Site is open year-round, but the best time to visit is during the spring and fall. During these seasons, the gardens are in full bloom, and the vibrant colors of the foliage provide a stunning backdrop. Additionally, the cooler temperatures make exploring the mansion and the grounds more comfortable.

To ensure accuracy, it is recommended to verify the information provided by cross-referencing multiple independent sources, such as the official website of the Vanderbilt Mansion National Historic Site, National Park Service publications, travel guides, and reputable history or architecture publications.