See inside Kykuit, a 40-room mansion in New York that once belonged to the richest man in the world

• Kykuit, a 40-room mansion in Sleepy Hollow, New York, belonged to the Rockefeller family.
• It was built in 1913 for John D. Rockefeller, founder of the Standard Oil Company.
• The property features an art gallery, sprawling gardens, and a collection of vintage cars.

At the height of his success, John D. Rockefeller's Standard Oil fortune comprised 1.5% of the gross domestic product of the United States, according to the Library of Congress. He was the world's first billionaire, with a net worth of $1.4 billion in 1937 (around $29.5 billion today), and the richest individual in the world at the time, according to Harvard Business School.

Kykuit (pronounced "kai-kit"), a 40-room Classical Revival-style villa in Sleepy Hollow, New York, was his idyllic seasonal oasis about 30 miles north of New York City.

Built in 1913, Kykuit belonged to four generations of the Rockefeller family before former New York governor and US Vice President Nelson A. Rockefeller left it to the National Trust for Historic Preservation after his death in 1977, according to the Hudson River Valley Institute. The estate opened to the public in 1991.

Today, visitors can tour the home and its lush gardens overlooking the Hudson River through Historic Hudson Valley. Tours are available from May through November and range from $25 to $75 depending on length. In May 2023, I took the Classic Tour, which lasted two hours and 15 minutes and cost $45 (the price has since increased to $55 for one adult ticket).

Take a look inside.

Tours of Kykuit leave from the Visitor Center, where I perused a gift shop with books about the Rockefellers and crafts by local artisans.

I checked in at the front desk and received a wristband.

A shuttle bus transports tour groups from the Visitors Center to the mansion — it's a quick five-minute drive.

As I disembarked the bus, I felt transported back in time by Kykuit's Classical architecture, which featured Roman gods, and its serene garden landscapes.

The lush wisteria growing up the sides of the mansion was imported from China in 1820, according to our tour guide.

Our tour guide also shared that Tiffany's created the glass torch lamps in the front yard.

Sculptures from Nelson A. Rockefeller's vast modern art collection decorated the front porch.

The raised step at the entrance was designed for the Rockefellers to easily disembark from horse-drawn carriages.

Our first stop inside the house was the Office, which featured a copy of a 1767 portrait of Benjamin Franklin that hangs in the Green Room of the White House.

I could picture the Rockefellers hosting fancy gatherings in the Music Room, the largest room in the home. It used to contain an organ, but the original grand piano remains.

However, John D. Rockefeller and his wife, Laura, were devout Baptists, so they didn't serve alcohol while entertaining guests in the Dining Room.

In the China Room, a set of dishes from Nelson Rockefeller's time as President Gerald Ford's vice president was embossed with "E Pluribus Unum" — "Out of Many, One" — which appears on the US' Great Seal.

A portrait of Abby Rockefeller, the wife of John D. Rockefeller Jr., hung in the Alcove with standing lamps designed by 20th-century Swiss sculptors the Giacometti brothers.

Kykuit's Library functioned as a family room, where the Rockefellers would gather after Sunday lunches, according to our tour guide.

I was surprised to find a full art gallery in the basement furnished with works by Pablo Picasso and Andy Warhol, collected by Nelson Rockefeller.

"Kykuit" comes from the Dutch word for "lookout." At 500 feet above sea level, the mansion's terrace provided gorgeous views of the gardens and the Hudson River.

Architect William Welles Bosworth designed different sections of the gardens to feel like different rooms, our guide said.

In one area, rows of linden trees were precisely manicured to create an allée, from the French word for "alley."

At every location on the grounds, I could hear the rippling sound of water fountains.

The last stop on the tour was the Rockefeller family's stables and garages, where they kept their stagecoaches and vintage cars.

With Kykuit's Classical architecture, impressive art collection, and manicured gardens, I felt like I was visiting a historic villa in Europe.