The big dome at the Church of St Charlemagne in Karlov is simply to die for.
Making a large building or a bridge requires a lot of complex math and engineering. But back in the Middle Ages and even after, these skills were pretty rudimentary. Sometimes architects would make a deal with the Devil to guarantee the quality of the engineering.
There are several structures in Prague where the Devil was the chief subcontractor. The last in our series of three devilish structures is the church at Karlov.
An ambitious design to honor Charlemagne
Emperor Charles IV did a lot to spread religion, backing the establishment of many churches and monasteries, and even collecting holy relics in an effort to interest the saints in casting their attention to Prague.
One church he backed was built in honor of Charlemagne, his namesake. The list of saints was a little loose and at the time, the French ruler was often called St Charlemagne despite never being duly canonized.
The Church of St Charlemagne in Karlov was built between 1351 and 1377, and still stands there on top of the hill looking over the Nusle Valley. The name Karlov is derived from the name Charles, and that is the colloquial name of the church as well as the neighborhood.
Most architects were a bit afraid of Emperor Charles’ ambitious concept and shied away from it.
Charles wanted a showcase building to honor Charlemagne, something with a unique design but inspired by the Aachen Cathedral, where Charlemagne has his tomb. Charles wanted a similar church with an eight-sided design, which was not typical for the time. The Aachen Cathedral was also where Holy Roman emperors were crowned.
A young architect was hoping to make a name for himself so he could finally marry the girl of his dreams, Anežka, the daughter of Prague burgermeister Václav z Rokycan.
The young architect’s name was Vít or Bohuslav Hedvábný. He thought if he could make the church, his reputation would be set for life.
Young Hedvábný came up with new ways to make such a dome, and the Emperor was impressed.
As the building rose, so did Hedvábný’s fortune, and he was winning the hand of his true love.
Construction carried on for many years. As the octagonal dome, unsupported by a central pillar, was being built the architect began to have doubts about it. The workers too voiced their concerns and became increasingly afraid of the work site. One of the main builders, named Jaroš, was also interested in Anežka and was secretly causing accidents on the work site.
One night, a strange man turned up and told the architect he could make sure that the dome would hold up, and the accidents would stop. The mysterious man then produced a contract to be signed in blood. His identity was no mystery though to anybody who was paying attention. It was the Devil.
The architect hesitated but eventually signed, thinking he could live a happy life with his sweetheart and then somehow weasel out of the deal later. Such is the folly of youth.
Once the dome was finished, none of the workers dared to remove the wooden supports and scaffolding, as no one believed it would stand without them. Jaroš had spread the word that it was unsafe to touch it.
But Emperor Charles IV was coming personally to see the result of his pet project. Something had to be done to make the site ready.
The architect could not remove the supports himself, but he had an idea. If he set the wood on fire, the supports would collapse and since the dome was made of stone, the fire shouldn’t damage it. If anything, the heat might make the concrete stronger.
The flames on the supports went up much faster and higher than he had expected. Then there was the noise of a tremendous crash and nothing but smoke and dust as far as anyone could see.
The architect was sure he had destroyed the church after decades of work, so he ran away as fast as he could. He ran so far that he went right in the Vltava river and drowned.
The Devil kept his word, though. The dome and the rest of the church were still standing and perfectly sound.
And the Devil kept something else — the soul of the architect.
And as for Anežka, she refused to marry Jaroš and joined the convent built next to the church. She was buried in the cemetery that used to be there.
A variation on the legend is that the architect did not run into the river but to a distant town where he joined a monastic order of silent monks to hide his shame at failure. Only after many decades did he learn that the dome did not fall.
He took leave to go and see the church, and there he discovered the grave of his loved one, who had died just days before he arrived.
The major problem with this very popular tale is that the dome is actually a much later addition to the church, which has undergone numerous transformations. The original design was unusual but was not as risky as the unsupported dome. The first roof was high hipped, and more like a funnel or a bugle standing upright.
The official website of the church recounts a version of the dome tale, but adds that while it is charming there is absolutely no chance that any of it is true. Their version leaves out the Devil and the suicide, but includes the fire and collapse.
Very little of the original design remains. Some Gothic elements are in the chancel, but the rest of the design is Baroque or later. And many additions were put on the building over the century.
The church was rededicated to the Assumption of the Virgin Mary and St Charles the Great in the late 15th century, presumably because Charlemagne’s sainthood was rather flimsy.
The star-shaped vault and dome was built in 1575, most likely by Bonifaz Wohlmut. He died in 1579, at the age of 69. Wohlmut also worked on St Vitus’ Cathedral and the Belvedere Summer Palace. He did not drown and was not a young man in love, so he is unlikely to be the source of the legend.
The vaulting is 22.8 meters wide and reaches a height of 17.7 meters, while the arches are only 20 cm thick and rest on walls that are less than one meter thick.
Other famed architects to work on the complex of buildings at Karlov included Giovanni Domenico Orsi and František Maxmilián Kaňka.
The church also now has a copy of the Holy Steps of the Lateran Church in Rome. The grotto under the steps has a five-section Bethlehem Cave with statues of the Holy Family in an annex built by Jan Blažej Santini Aichel.
The church was briefly deconsecrated between 1785 and 1789, during the religious reforms of Emperor Joseph II.
The church is only open to the public for a few hours every Sunday. The adjacent cloister is now the Police Museum and is open on a more regular schedule, for those interested in crime scene replicas and evidence from famous cases, such as an axe from an axe murder — and the authentic cracked skull of the victim.
The cannon balls in the church facade come from the Seven Years’ War, from 1756 to 1763, The church was attacked in 1757 by Prussian troops of Emperor Frederick II and was heavily damaged, but the dome remained unharmed.