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Our guide to underground Copenhagen


Have no fear! This is not an article about conspiratorial Copenhagen politics – we would just like to tell you about some of the city’s attractions if you drop down from street level to take in some of the treasures hidden below. While the city bustles above, you can find mysticism and treasures and see new angles of Copenhagen.

Start with a tour beneath Christiansborg Castle and explore the ruins of Absalon’s Castle from 1167 or visit Cisternerne, once the subterranean reservoirs that supplied the city’s water.

Here are our favourite underground experiences in the Copenhagen area.


The outer wall of Bishop Absalon’s castle, built in the 12th Century, comprises the largest and oldest ruin beneath Christiansborg Castle, built as a defence against attacks from the Vends (Baltic pirates). The other major ruin beneath the Castle is the foundations of the infamous Blue Tower, which was the highest of Copenhagen Castle’s towers. Used to incarcerate political opponents and notable criminals, the tower’s most famous prisoner was King Christian IV’s daughter, Leonora Christina, imprisoned for 22 years by order of King Frederik III.


Beneath the green, pleasant landscape of the Søndermarken Park in Frederiksberg, you can discover the cavernous stalactite caves that form the basis for establishing the reservoirs here. Once there were some 16,000,000 litres of drinking Water stored here: the water is now gone, replaced by art exhibitions and other functions, the inspiration for which is the unique climate and the unusual architectonic quality of the caves.


The English Royal Navy’s bombardment of Copenhagen at the beginning of the 19th century signalled the start of the construction of Copenhagen’s fortifications. It proved however, to be of little or no use and has since had little use other than as a recreational area. Recently, however, it’s potential to provide treats of both the cultural and natural type has brought new life to the fortifications, perhaps best experienced at the western ramparts (Vestvolden) in Hvidovre and at the offshore fortress, Trekroner, which you can reach by waterbus from the Kvæsthus Wharf on Saturdays and Sundays.


The underground chambers of the treasury at Rosenborg Palace house, within their metre thick walls, the three regal crowns (2 crowns for kings and one crown for queens!) together with all the other royal regalia. The crowns are notable for their sumptuous decorations with precious stones and gold ornamenting. The regalia consists – primarily – of four sets – a brilliant-diamond set, a rosecut diamond set, a pearl/ruby set and an emerald set – which contains some of the world’s finest emeralds.

The statue of Holger Danske


Built on a low rise, Kronborg Castle commands excellent views of the narrow straits between Denmark and Sweden. The fortifications, first and foremost the breastworks and the casemates, were intended as the first line of defence for eastern Denmark and the castle was also home to the Royal Family until the late 17th century.

Amongst the castle’s many attractions, is the statue of Holger Danske – Denmark’s mythological protector – who has stood watch over the nation in the cold casemates for several centuries. The saga maintains that, if foreign enemies threaten the country, the statue transforms to a warrior of flesh and blood and Holger Danske will again ensure the safety of the nation!

To reach Kronborg Castle, you can take the train from Copenhagen to Helsingør: The nearest station is the Østerport Station, about 20 minutes’ walk from the Copenhagen Admiral Hotel.