Whimsical Victoriana, endless animal carvings, and a lavish interior design make Cardiff Castle as strange as it is captivating.

Prince Harry and Meghan Markle
Credit: Joe Giddens/PA Images/Getty Images

What’s it like to live in a city with a 2,000-year-old fairy-tale castle at its center? Meghan Markle will find out this Thursday when she visits Cardiff Castle in the capital of Wales with fiancé Prince Harry.

In one of the couples’ first public duties, the actress and fifth (and soon to be sixth) in line to the British throne will spend Thursday looking around a medieval castle that became a bizarre Victorian Gothic revival mansion. Meghan might feel like she's back on a film set — and she will be; the BBC have filmed both “Doctor Who” and “Sherlock” here.

Exterior of Cardiff Castle
Credit: Jamie Carter

Cardiff Castle was originally a Roman Fort, though the oldest part is now an 11th century Norman castle as well preserved as any in Britain. However, the real attraction is the bizarre Gothic transformation of a 15th-century mansion, which took place here during the 19th century when the castle was owned by John Crichton-Stuart, the 3rd Marquess of Bute. He was then one of the richest men in the world. His family made Cardiff the world's biggest coal port, and the Marquess gave architect William Burges whatever funds he needed to create one of the most lavish interiors in Britain.

Stuffed with intricate wood carvings depicting everything from Greek and Roman mythology to Aesop's Fables and the Zodiac, Cardiff Castle is now packed with Victorian Gothic strangeness.

Interior of Cardiff Castle
Credit: Jamie Carter

Meghan and Harry will definitely grace Cardiff Castle's banqueting hall and library, two of the grandest rooms. They will be just the latest A-listers to grace the long table in the banqueting hall: Previous visitors include the Queen, who held a dinner here for a NATO meeting in 2014, attended by President Obama.

Other visitors include Nelson Mandela, Pope John Paul II and golfer Tiger Woods (the Ryder Cup dinner was held here in 2010). Its fireplace doubles as a model of a medieval castle. Reached via the great Octagon staircase, whose baluster is topped by a gilded alligator chasing a cherub, this site of an old medieval hall feels almost church-like.

Interior staircase at Cardiff Castle
Credit: Jamie Carter

Down the staircase — via a statue of a lion in full armour with a dragon on its head, and a carved monkey stealing an apple from the Tree of Knowledge — is the warmer, wood-paneled Library.

The Royal couple will surely also visit the Arab Room, a Moorish fantasy room who impossibly intricate ceiling is decorated with around $11 million of gold-leaf. Here in the main 15th century part of the castle, the room is supposed to resemble where an Arab ruler's harem would live.

Perhaps the weirdest section of Cardiff Castle is the Clock Tower. It dominates the castle, and Cardiff itself. Inside is an eccentric suite of rooms designed to be a bachelor pad for the young Marquess. On the lower level is the extravagant Winter Smoking Room, its theme being “time” — the walls and ceiling contain images of constellations, the zodiac, cardinal points, and carved sunrises and sunsets. There are also cigar drawers and a drinks cabinet.

Detail of exterior and statue at Cardiff Castle
Credit: Jamie Carter

However, the highlight is at the top of the tower, where the two-level Summer Smoking Room gives views across the city in all directions. Fittingly, it's all about the cosmos, with a grand tiled floor depicting the geocentric model, and walls containing figures of astronomers and Greek gods. The Marquess never did hold his bachelor party in such opulent surroundings, as intended — he got married just before the castle was finished.

Below the tower is the busy center of Cardiff, a bustling city whose exquisite Victorian and Edwardian a shopping arcades contain tea houses, interior stylists, vintage tailors and boutique food shops (and “The New York Deli,” in case Meghan needs a hoagie, bagel or a hot dog). Also below is the castle’s defensive Animal Wall hosting a stunning line-up of 15 carved stone statues including lions, bear, hyena, leopard, anteater, and raccoon.

What will Meghan think of one of Britain’s grandest and oddest buildings? There may be little that’s either Royal or Welsh about Wales’ most captivating castle, but Megan and Harry are in for a grand day out.