See inside Oheka Castle, the 127-room Long Island estate that inspired 'The Great Gatsby'

Oheka Castle, the second-largest private home in the US, has been through a lot over the last 100 years. It cost $40 million to restore in the '80s.

• I took a tour of Long Island's Oheka Castle, an hour west of Manhattan.
• It's the second-largest private home in the US and was built in 1919.
• It's now a residence, hotel, restaurant, and events venue.

If you've ever read or seen "The Great Gatsby," you know 1920s New York was home to extravagant mansions with owners who hosted lavish parties.

One of those owners was financier Otto Hermann Kahn, who built Oheka Castle — named after its owner (Oh-He-Ka) — on Long Island in 1919.

Kahn's wife used to call the home "Otto's zoo," and that seemed to be an accurate description. A-listers of the time used to party at the 109,000-square-foot home, with Kahn as a Gatsby-like figure entertaining all his guests.

But Oheka's journey didn't end there. After Kahn's death in 1934, the property changed hands numerous times until it was abandoned in the '80s. Fires, vandalism, and theft devastated it.

According to Oheka Castle, land developer Gary Melius then purchased the estate and spent $40 million restoring it to its former glory.

Today, it's the second-largest private home in the US, behind only Biltmore House in North Carolina. It's a popular venue for weddings, a restaurant, and a hotel, and has been featured in movies, TV shows, and music videos. Taylor Swift even filmed the "Blank Space" video there.

You can also tour the grounds for $30.

I took the tour and was astonished by the beauty of Oheka Castle. Here's what it was like to visit.

Oheka Castle was built in 1919 by German-American financier Otto Hermann Kahn.

He paid approximately $11 million, or over $158 million in today's currency, for 443 acres of land in West Hills, New York.

Oheka Castle has been through a lot in its 100-plus years of history, and for anyone who wants to learn more, there are tours offered twice daily.

So, I decided to visit. All I knew about Oheka was that Kevin Jonas got married there and Taylor Swift filmed the "Blank Space" music video there.

But Oheka has a rich history. I learned all about it on a beautiful April afternoon.

When you drive to the entryway, it's a bit intimidating. There's someone working the gate who must let you in.

Then comes a long driveway. I felt like I was going back in time to the Gilded Age.

My first look at the main house was astounding — and yes, I mean house. Oheka Castle is the second-largest private residence in the US.

It's also on the National Register of Historic Places. It was added in September 2004.

When Kahn built this house, he had three requirements: He wanted to be high up, he wanted a view of the water, and he needed the house to be fireproof.

His previous house in New Jersey had burned down in a fire. Oheka, in contrast, is built entirely out of stone.

I went inside and waited in front of a grand staircase with the rest of my group for our tour to begin.

When it began, we saw photos of what the house looked like before it was restored by its current owner. We'd learn more about this later.

The first room we entered was this beautiful entryway with a mural of the sky on the ceiling.

The house itself is 109,000 square feet and has 127 rooms.

Many of the rooms are dedicated to showing off the home's history, like the Chaplin Room.

Charlie Chaplin was just one of the many '20s A-listers who hung out at Oheka. This photo shows Chaplin (right) with Kahn (center) and actor Douglas Fairbanks (left).

In fact, according to my tour guide, Jay Gatsby's wild parties in "The Great Gatsby" were inspired by what was going down at Oheka in the '20s.

This was Kahn's wife Adelaide's favorite room. Adelaide wasn't as big of an entertainer as her husband, but this sunny room was perfect for guests.

This ballroom is the only room that's not original to Kahn's time inside Oheka today.

But as you can see from the ballroom's windows, Oheka met Kahn's requirement for a view of the water. He used to dock his yacht there.

Kahn, who was Jewish, also built a golf course on his property — country clubs at the time wouldn't admit Jewish people or allow them to play.

After Kahn's death in 1934, the property was shuffled between owners. From 1948 to 1979, it was the Eastern Military Academy.

During those days, what is now the breakfast room was used as a gym.

From that room, we made our way to this huge library.

A portrait of Kahn hung above the fireplace.

Our final stop on the first floor was this room, which also houses a bar. Press clippings about Oheka adorned the walls.

Among the displayed articles was Danielle and Kevin Jonas' wedding spread in People. They got married at the estate in 2009.

Then we went upstairs to check out the hotel and bridal suite.

The bridal suite, which is on the fourth floor, opens with this mural-covered entryway.

A beautiful open room with windows allows wedding parties to take in the view of Oheka's well-manicured grounds.

The gardens at Oheka are breathtaking from above.

Here's the main bedroom of the bridal suite.

The primary bathroom has a bathtub and shower.

Then it was time to check out the gardens — and to learn what happened to Oheka.

When the Eastern Military Academy went bankrupt and vacated its premises in 1979, Oheka was left abandoned.

Residents who lived nearby were concerned about vandalism. One neighbor even took this statue for safekeeping and returned it when Oheka was restored in the '80s.

Land developer Gary Melius purchased Oheka in 1984 and spent $40 million restoring it to its former glory.

The gardens were originally designed by the Olmsted Brothers, best known for helping with Central Park.

Melius used those original sketches to restore Oheka.

These statues were tracked down at an auction and are thought to date back to the Renaissance.

Now, it's a beautiful wedding venue, hotel, restaurant, and home — Melius keeps an apartment on the third floor.

As I left the grounds, I got one more look at the restaurant and its courtyard.

I would highly recommend taking a tour of Oheka. As I viewed its stunning surroundings and learned about its unique history, I felt like I was traveling back in time.