Part of the Czech Crown Jewels from Charles IV
The orb from the Czech crown jewels. 1300’s

Charles IV of blessed memory, Holy Roman Emperor and King of Bohemia, looked out from Prasky Hrad, (Prague Castle) his beautiful home in the Golden City of Prague, above the Vltava, and watched the small boats and river rafts plying the water above the ruins of Juditin Most, the Judith Bridge, which had been destroyed in a flood some years earlier (1342). He had a desire to spend some money to make the lives of his people easier and here was a good place to start.

It was a struggle now to cross from Mala Strana (Lesser Town) to the other side of the river Staro Mesto (Old Town) where so many people lived. It was hard on the farmers, bringing their produce to the markets, because they had to hire boats to cross and sometimes couldn’t make it to the far side at all. It was hard on people who lived on one side but worked on the other, hard for citizens to get to shops and markets that sold what they needed. Just the normal winter water levels made using boats very difficult and they really couldn’t carry enough of what was necessary and when there were floods, everything stopped. It was time to fix that.


What was needed was a new bridge to let people and carts cross dry-shod no matter what the weather, a magnificent bridge that would stand for centuries, protected by splitters that would stand upstream of the bridge pilings to fend off ice and debris that might damage them. No, that wasn’t good enough. The bridge would have stone arches deeply set into the riverbed to make it stronger, not pilings that would crumple when hit with floodwaters, so that floods could not wash them out. Kamenný Most it would be called, the Stone Bridge.

It would be made of the finest materials: hard stone that wouldn’t wear away, mortar of the best lime and sieved sand to make it regular, and eggs to make the mortar the strongest it could be. That was going to take a lot of eggs,

So plans were made. Astrologers were consulted. An architect was assigned. Charts of the materials that would be needed were drawn up. Wagons were gathered and more built for the transport of materials. Workmen’s quarters were thrown up to house the hundreds that would work on the bridge, with stables to house the working animals. Orders went out from the King to the far corners of Bohemia, Morava, Silesko (Bohemia, Moravia and Silesia, the provinces of the Czech crown) and even farther for workers, stone, logs, limestone, coal, sand, and eggs, fodder for the horses, food for the workers and more and more.


A beautiful founding stone was cut and the roadways were cleared and at 5:31am on 9 July 1357 the first stone was laid by Charles IV himself. This specific time, a palindrome (1357 9/7 5:31), was proper for the bridge, and would give the stone bridge additional strength since it would be echoed in the geometry of the arches that formed the base.

Women were hired to staff the kitchens, making food for those who worked on the project, and to carry water and beer to the workers. They also did all the lighter tasks of counting stones, determining the quality of the materials, laundry, finding appropriate weights of loads so as not to overburden transport. Women did all the tasks that didn’t take sheer muscle, and often drove carts and wagons when drivers were scarce.

lime kiln diagram with labels by M Jaen

Lime kilns were built to burn the limestone into quicklime, along the riverbank downwind of the city and in areas where breezes blew, so no one would be blinded by the fumes. Coal and limestone began to pile up by the kilns to be layered in and cooked. Men were hired to rake the cooked rock into pools of river water to quickly cool. More men would then drag the cooled rock to a drying area and later to a grinding shed where the stones were reduced to powder and shoveled into sacks. Wagons began rolling the slaked lime to the construction site as soon as the first batches were ready.

Areas along the river with good sand were marked and cartsful began to head for the construction site. Trees were cut to make sheds to protect materials and for workspaces, and hay and straw for thatch, to keep roadways from turning into muck pits, to make scaffolding and the temporary cofferdams that made it possible to set the arches on bedrock below the river after sand and muck had been dug away.

Huge settling ponds were constructed so that clean water would be available to make the best mortar, and sieves for sifting sand. Finally eggs began to arrive in huge wagonloads, cushioned in sand and straw.


Logs were piled on Kampa Island on both sides of the Čertovka channel, and even on the riverbank below the castle. Stones were cut and brought to flat areas on both sides of the river, to be moved to the river bank when there was space. And the heavy construction work began.

The cofferdams went in and water was drained, and sand and muck were lifted, bucket by bucket, to be dumped into carts and taken to the Jewish Quarter, the area now called Josefov, which kept flooding every year. First and embankment, a levee as built and then the carts just dropped on load after another on the streets and around the homes. The area had been raised somewhat, a few centuries before, but this would help to keep it drier than it had been.

Finally stones were being lowered into the coffer-dammed and pumped areas and mortar mixed. The slaked lime, sifted sand, clear water. and eggs went onto floors, as the sheds were called, where the mortar was mixed with large rakes and set into buckets to be carted to where the stones were being laid. Women were hired to sort the eggs from the sand and straw and they would toss the eggs, shells and all, into the mix. The carts of leftover sand and straw went to the stables, and the muck piles from there went to farm fields, and then they went for more eggs.

Bit by bit, stone by stone, the foundation of the first arch went in. As quickly as it poked above the water level, the cofferdam was moved to the spot for the next foundation, the pumps started up, the muck shoveled away, and on and on. Fifteen times to build the bases of the beautiful arches that hold even now!! The splitters were built and the space between the arches filled in and on, and on….

…and more sand and more water and more lime and more eggs arrived, and trees to make more shelters and stone and workers to replace those who had to go home…. and more carts of supplies and food….


Now, all those eggs came from farms from all over the country. A wagon would be sent to a village and the number of eggs required would be announced. With much grumbling – but also gratitude that it was eggs and not money that was required! – the wagon would be filled until the amount specified was reached, the time for the next load announced and then the wagon would roll back to the Golden City of Prague.


There was one village where the inhabitants were really worried that eggs were so breakable and perishable. Wasn’t that going to be a problem? The driver of the cart didn’t know, so they did their best and the required number of eggs rolled to the mortar mixing area.

The first eggs of the load were tossed onto the mixing floor, smashed with the rakes and everyone had to look twice. When they realized what they were seeing, a roar of laughter went up and repeated through the working area as people ran to tell others about the solution that this one village came up with. The eggs were hard boiled!!!!!

So everyone ate well that evening, but the village never lived it down and is still called Vaječný hrad, which means “egg castle.”


When the bridge was finished after several years of hard work, it is said that Charles ceremonially ate a hard-boiled egg as part of the celebration. Leftover materials went to repair or strengthen structures along the river, and for many other purposes. At least one of the lime kilns continued making its product that was still used in mortar, but also in the public cemeteries to keep them “sweet” rather than haunts of rats and disease.

Charles IV went on to create Hladová zeď (the Hunger Wall) during a time of great famine, hrad Karlštejn (Karlstein Castle), for the protection of the Czech crown jewels, and the beginnings of Katedrale Sv. Vitus (Cathedral of St. Vitus), among other public works.

By Packare – Own work, CC0,

And when our blessed King had long since gone to his reward, the bridge was re-named Karlův Most (the Charles Bridge) in his honor.

The bridge construction kept on going for most of another century to finish all the details and it has needed repairs, balustrades, statues, lamps, and other details down through the centuries. But for most of seven hundred years this bridge has stood, connecting the two sides of the city, thanks to hard work, and to eggs.

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logger-motif work craft

barrel-roll-motif work craft

Note – An old Czech proverb is that an idea is easy until you start to build. This definitely applies to the Bridge!

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Rich Kolar – Happy 665th Birthday to the Charles Bridge – July 9 – By the time I post this it is almost the next day in Prague, but here in the Chicago area where I’m at I can celebrate this wonderful bridge’s birthday for another few more hours.
So this is the next in sequence of the photos I took on our first full day in Prague on May 24, 2022. After taking some pre-sunrise photos a block or so away by our apartment, I walked over to the bridge, which at 4:50 a.m. had a few people wandering on it, but just being a bit patient or moving a bit with my camera I was able to get off a few photos with nobody else in it.
This is looking toward Old Town. If you look closely on the right hand side of this photo you will see a few swans floating in the river and the crescent moon in the upper right.070922 Karluv Most

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The Notre Dame Cathedral isn’t the first major European landmark to suffer damage; here’s Prague’s Charles Bridge after the 1890 floods 😮


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More to study

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The BBS series “Secrets of the Castle” has a lot of sections that apply and it’s fascinating in its own right. Guedelon is in France. This is a 25-year experimental archaeology project that’s finally getting close to completion. (more will be added to this section)

Episode 1 – Building A Medieval Castle Using Authentic Tools – – Cutting stones after 8:30. Workers’ homes 11:00. A few glimpses of mortar making after 16:00. Section on mortar begins at 21:45. Setting stones 25:30. Fitted stones at 30:00. Cutting finer stone 40:30.

Episode 2 – The Art Of Medieval Combat: Defending The Castle –

Episode 3 – The Colourful World Of Medieval Castle Painting –

Episode 4 – The Sophisticated Stonemasonry Of The Medieval Castle – – Cutting stone around 7:00, Shaping stone 8:00,

Episode 5 –

Episode 6 –

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Charles Bridge images

Fotograf Milan Bachan

(more will be added to this section)

Divider from a photo by Sergey Ashmarin, found on Wikipedia

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Note – So that you know, this is accurate as far as construction techniques, but the eggs are legendary. No one is certain how, why, or if they were actually used in the mortar! Vaječný hrad (Egg Castle, yes the “castle” part is a sneer….) doesn’t appear on any map, either, but everyone knows that it still exists and everyone has a different idea of where. 🙂

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Page Published 10/9/21 (C) M. Bartlett
Last updated 8/15/22