I've toured 8 historic Gilded Age mansions. Here are the most extravagant displays of wealth I've seen.

The Breakers, a Vanderbilt mansion in Newport, Rhode Island, is famous for its size and opulence.

Cornelius Vanderbilt II was the grandson of Cornelius Vanderbilt, the richest man in America during the Gilded Age, and succeeded him as the president and chairman of the New York Central Railroad.

Cornelius Vanderbilt II and his wife, Alice Vanderbilt, built The Breakers, a 70-room, 138,300-square-foot summer "cottage," in 1895.

It was named "The Breakers" because of the way the waves would break on the rocky shores of the oceanfront property.

The wrought-iron and bronze light fixture in the billiard room was so heavy that it needed to be attached to the house's structural beams.

The design of the billiard room was inspired by ancient Rome with handcrafted marble mosaic ceilings and floors.

The morning room, designed by French decorator Jules Allard, featured platinum panels in the walls depicting Greek Muses.

Conservators assumed that the panels were silver, but they never seemed to tarnish. Testing with a portable X-ray machine showed that the panels were actually made of platinum, one of the most valuable metals in the world.

The Vanderbilts acquired the stone fireplace in the library from a 500-year-old French chateau.

The Vanderbilt family used the library as a place to spend their leisure time playing card games and drinking tea.

The wood panels on the library walls were pressed with gold leaf to make them look like the leather cover of a book.

The ceiling of the Library was also gilded with gold.

Cornelius Vanderbilt II's bathtub was so thick that it needed to be filled and emptied several times to stay warm.

The tub was carved from one block of marble and designed to look like a Roman sarcophagus.

William K. Vanderbilt, Cornelius Vanderbilt II's brother, built Marble House in Newport as a gift for his wife Alva Vanderbilt's 39th birthday.

Completed in 1892, Marble House measures 140,000 square feet and has 50 rooms. The construction alone cost $11 million in 1892, or around $380 million today when adjusted for inflation.

After the couple divorced, Alva Vanderbilt hosted rallies for women's suffrage at the mansion with a set of dishes painted with the words "Votes for Women."

True to its name, Marble House was furnished with 500,000 cubic feet of marble that cost $7 million, or around $241 million today.

Alva Vanderbilt chose a golden-brown Italian marble for the floors, walls, and grand staircase.

The purple marble walls in the dining room were created from single slabs cut in half lengthwise in a process called bookmatching.

The Vanderbilts imported the purple marble from Algeria.

The dining-room chairs weighed 75 pounds each — so heavy that a footman had to help move them to seat guests.

The chairs were made of bronze and gilded with gold. The design was inspired by King Louis XIV of France's dining-room chairs.

Alva Vanderbilt purchased an entire art collection as a set to furnish their "Gothic Room."

Buying an art collection "en bloc," or as a set, instead of accumulating separate pieces over many years was a popular practice in the Gilded Age. Alva Vanderbilt purchased hers from Emile Gavet, a French art collector.

The walls of the home's Grand Salon were covered in 22-karat gold leaf.

The Grand Salon, also known as the Gold Room, functioned as the Vanderbilts' ballroom where they hosted lavish parties and balls.

In addition to importing marble and furniture from abroad, the Vanderbilts also planted European copper beech trees on the grounds.

European copper beech trees can grow up to 45 feet wide.

Rosecliff in Newport was the summer home of Theresa "Tessie" Fair Oelrichs, a silver heiress.

Oelrichs' father, James Fair, discovered the largest lode of silver ore in the US and became known as the "Bonanza King."

Oelrichs and her husband, Hermann Oelrichs, spent $2.5 million building Rosecliff — the equivalent of around $91 million today. It was completed in 1902.

Rosecliff's most distinctive feature is its ballroom — the largest single private room in the entire town of Newport.

The ballroom measures 40 feet by 80 feet. Its size and opulence have made it the perfect backdrop for movie scenes in films such as "The Great Gatsby," "27 Dresses," and "Amistad."

Coal magnate Edward Julius Berwind and his wife, Sarah Herminie Berwind, built The Elms in Newport in 1901.

Edward Julius Berwind had a net worth of $31.4 million when he died in 1936 — around $774 million today when adjusted for inflation.

The Elms was modeled after an 18th-century French château named Chateau D'Asnieres and built on a 10-acre estate.

The Elms featured a conservatory, an indoor garden escape with a fountain and French statues.

The statues carved by Guillaume Coustou were sourced from Chateau D'Asnieres, which inspired the architecture of The Elms.

The dining room was full of priceless paintings from a Venetian palace, some so large that they spanned most of the wall.

The paintings showed scenes from battles led by Roman general Scipio Africanus. The dining room also featured a gilded ceiling.

The Berwinds devoted their breakfast room to displaying decorative panels from 18th-century China.

Displaying artwork collected from other countries or even setting aside an entire themed room for such artifacts was how Gilded Age families signaled that they were worldly and well-traveled.

Beginning in 1852, Chateau-sur-Mer in Newport housed three generations of the Wetmore family.

William Shepard Wetmore made his fortune as a merchant importing goods from China and built the first version of Chateau-sur-Mer in 1852. His son, George Wetmore, served as governor and a US senator of Rhode Island. He and his wife, Edith Wetmore, hired Richard Morris Hunt to remodel the home in the 1870s.

A giant mirror in Chateau-sur-Mer's ballroom served as a status symbol due to the high price of large plate glass.

The mirror reflected light from the room's glass lamps during balls.

The wallpaper in the dining room was made of Spanish leather covered in silver.

The silver wallpaper, stamped with flowers and vines, shone with light from the dining room's flickering lamps in its heyday. It has since tarnished.

Like the Berwinds' breakfast room at The Elms, Chateau-sur-Mer included a "Turkish room" where the Wetmores displayed international Islamic art.

"Turkish" art was a catch-all term for art inspired by the Middle East and Asia — a popular design trend in the 1870s.

Lyndhurst Mansion in Tarrytown, New York, belonged to three elite Gilded Age families.

Former New York City mayor William Paulding Jr. built the Lyndhurst Mansion in 1842. It was then bought by a merchant and inventor named George Merritt. Jay Gould, a railroad tycoon who was one of the wealthiest men in the Gilded Age, purchased the property from the Merritt family.

The walls in the entrance hall looked like marble but were actually handpainted plaster — an unlikely symbol of wealth.

The handcrafted faux marble walls served as a status symbol because they were more expensive to produce than real marble.

The walls in the dining room at Lyndhurst Mansion featured more faux finishes.

The walls were stenciled by hand to look like they were covered in leather wallpaper, and the columns on the fireplace were painted to match the real red-grain marble.

Jay Gould's daughter, Helen Gould, built a bowling alley on the grounds of Lyndhurst Mansion in 1894.

The bowling alley still works and can be rented out for private events.

Staatsburgh, a 79-room mansion in Staatsburg, New York, belonged to socialite Ruth Livingston Mills and her financier husband, Ogden Mills.

Staatsburgh was completed in 1896 and spans 30,000 square feet.

Around 95% of the furniture, artwork, and other items on display are authentic to the home and the Mills family.

At Staatsburgh, the dining room floor was made of 1-inch-thick Vermont marble to quiet the sounds of the kitchen below.

The walls were also decorated with green Italian and French marble and Belgian tapestries from the 18th century.

In Staatsburgh's drawing room, the Millses displayed three ancient Greek urns dating from around 400 to 600 BCE.

The urns were the oldest artifacts in the room.

Frederick and Louise Vanderbilt built their 54-room mansion in Hyde Park, New York, in 1898.

Frederick Vanderbilt was another grandson of Cornelius Vanderbilt.

Cornelius Vanderbilt II, who built The Breakers, and William K. Vanderbilt, who built Marble House, were his brothers, as was George Vanderbilt, who commissioned North Carolina's Biltmore House, the largest private house in the US.

Frederick and Louise Vanderbilt spent $660,000 to build their Hyde Park estate, which would be over $23 million in today's dollars.

Their dining room featured one of the largest Islamic carpets in the world.

The carpet measured 20 by 40 feet and was over 400 years old.

The railing of the grand staircase was upholstered with velvet.

The Vanderbilts missed no details in making every aspect of their home a luxurious experience.

As I've toured all of these mansions, I've felt transported to European palaces.

Wealthy members of Gilded Age society thought of themselves as America's royalty and decorated their homes accordingly.

I haven't been to much of Europe, but now that I've visited these eight mansions, I have a pretty good sense of what it would be like to tour a French palace or Venetian art museum.