(CNN) — Many modern visitors to Denmark are drawn by its groundbreaking Nordic cuisine, beautiful design, clean cities, windswept coastline or its cycle network -- all of which help make it one of the happiest countries on Earth.

But there's another, older, set of travel attractions that make it worth visiting: castles.

A kingdom to this very day, this small Scandinavian country has an impressive collection of palaces ranging from abandoned island fortresses to Shakespearean royal dwellings, elegant water castles and countryside regal retreats.

Here are some of the best that Denmark has to offer.

Kronborg

Kronborg: The "Hamlet" castle Jon Nordstrøm/Courtesy of VisitDenmark

Something may have been rotten in the state of Denmark, according to Shakespeare's "Hamlet," but that decay hasn't touched the grandiose castle that featured in the play.

Kronborg, in the city of Helsingør, was immortalized by the English playwright as Elsinore, the setting for much of his epic royal revenge tragedy.

It is at the battlements here that characters Marcellus and Horatio had their oft-quoted "something is rotten" conversation. It's a cool location for Shakespeare fans to check off their list, but an amazing place to explore even for folks who haven't read or seen the play.

The spectacular UNESCO-protected fortress stands over the narrow Øresund sound, just four kilometers across the water from Sweden. It's filled with mysterious pathways, halls and dungeons.

Constructed in the 15th century as a vital border point for the ships traveling via the sound to and from the Baltic Sea, it was once one of the most prominent and powerful castles in Europe.

Kronborg , 3000 Helsingør; +45 49 21 30 78

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Frederiksborg

Anyone who likes their castles postcard-perfect will love Frederiksborg.

What can be more picturesque than a large Renaissance palace on the water surrounded by lovely Baroque gardens?

Frederiksborg was the first Danish castle to be built inland and was always destined for recreational rather than defense purposes, which explains the fairytale looks.

Numerous towers, fountains, statues, turrets and spires enhance its charming allure.

Inside is the largest portrait gallery in Denmark as well as an enticing maze of decorated halls.

Frederiksborg , 10, 3400 Hillerød; +45 48 26 04 39

The Hermitage

The Hermitage was originally a hunting lodge located inside the Deer Park. Kim Wyon/Courtesy of VisitDenmark

Technically not a castle but a hunting lodge, The Hermitage is nevertheless an indisputable part of Danish castle heritage.

What makes this area truly unique isn't necessarily the architecture of the lodge itself -- although it's a lovely miniature Baroque palace that hosted banquets during royal hunting escapes.

The thing that makes The Hermitage stand out is the landscape it's set against.

In 2015, UNESCO inscribed the Dyrehave (or Deer Park) surrounding the lodge into its World Heritage list as a classic hunting landscape of North Zealand. It's still richly forested.

Today the deer are no longer hunted in the Dyrehave. Instead, they mingle with forest visitors, adding to the magical fairytale atmosphere.

The Hermitage , 2800 Lyngby; +45 33 92 70 85

Amalienborg

London has Buckingham Palace, Copenhagen has Amalienborg.

Both have queens in residence and both countries are constitutional monarchies.

Both palaces are guarded by busby-wearing soldiers, to the delight of tourists.

What's different is that Amialienborg consists of four identical buildings designed initially for the noblemen of the Danish capital.

The royal family moved here at the end of the 18th century after a fire that destroyed their old home at Christiansborg Palace, which is now the seat of the country's government (see below).

Amialienborg opens to the public from time to time, allowing visitors to see how the queen and king live.

Otherwise, there's a spectacular view on the Marble Church from the center of the square and the Little Mermaid is a few blocks away.

Amalienborg , 5, 1257 Copenhagen; +45 33 12 21 86

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Fredensborg

The fairytale-looking Fredensborg is a popular celebration venue for the royal family. Kim Wyon/Courtesy of VisitDenmark

Fredensborg may well be the castle that the Danish royals love the most.

Queen Margrethe celebrates her birthdays here, Queen Mother Ingrid made it her private residence, Princess Benedikte had her wedding in the palace chapel and it's used as a spring and autumn home by Crown Prince Frederik and Crown Princess Mary.

With its reserved but beautiful looks, infinite Baroque gardens, lush surrounding forests and peaceful setting, it's easy to see the appeal.

There's a sense of the royal retreat too. The gardens are open all year round and the palace can be visited on special occasions, so it's worth keeping an eye on its website.

Fredensborg Palace , Slottet 1B, 3480 Fredensborg; +45 33 40 31 87

Christiansborg

There is a place in Copenhagen unlike anywhere else in the world. Located on the central islet of Slotsholmen, Christiansborg Palace is the only building on Earth that houses all three official branches of power: executive, legislative and judicial.

While it may sound quite a risky idea to put everybody in the same place, Denmark's success story as a country seems to prove otherwise.

It's also known as "Borgen," ("the castle"), a name it shares with an internationally popular Danish political drama set in and around Christiansborg.

Royals also have their corner here, hosting receptions and meetings with the official delegations.

There are Royal Stables, the Tower with the best (and free) views over Copenhagen, the Palace Chapel and ruins of two former castles underneath.

You can visit some parts with a guided tour.

Christianborg Palace, Prins Jørgens Gård 1, 1218, Copenhagen; +45 33 92 64 92

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Rosenborg

Rosenborg is now a museum that houses a fascinating collection about the royal family. Kim Wyon/Courtesy of VisitDenmark

While many Danish castles are still all about the current royal family, Rosenborg takes visitors on a journey to discover all about the country's regal past.

This Renaissance architecture jewel in the center of Copenhagen is, in fact, a museum exhibiting the fascinating Royal Collections.

These include the Crown Jewels and Regalia, a Coronation Carpet and the Throne Chair of Denmark -- which you can see, but not sit on.

Apart from the splendid exhibits, the walk through the numerous richly decorated halls and pathways of the castle are an architectural feast.

Rosenborg , Øster Voldgade 4A, 1350, Copenhagen; +45 33 15 32 86

Egeskov

With moats and drawbridges, spacious courtyards and pretty gardens, Egeskov has genuine fairytale looks.

Conveniently and romantically located in the middle of the country's southern Funen region, this place is one of Denmark's many privately owned castles.

Inside are well-maintained interiors plus Titania's Palace, an impressive 3,000-piece dollhouse hand-built by the Irish company James Hicks & Sons at the beginning of the 20th century.

The palace also has a classic car exhibition featuring more than 50 vehicles of different eras.

Several hedge mazes offer the chance to get completely lost on the castle's premises.

Egeskov , Egeskov Gade 18, 5772 Kværndrup; +45 62 27 10 16

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Hammershus

Towering over the rocky cliffs of the North tip of Bornholm island lies the epic Hammershus, considered to be the largest medieval fortification in Northern Europe.

Although now in ruins, the walls of this fortress tell countless stories of Baltic crusades, fierce battles and daily life in the Dark Ages.

Today this vast complex serves as a perfect backdrop for enjoying the magnificent landscapes of rural Bornholm, as well as dramatic views over the Baltic Sea.