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Inside the alchemy laboratory of the Speculum Alchemiae museum.

Speculum Alchemiae: Secret Underground Alchemy Lab Discovered in Prague During Flood


The city of Prague, the capital of the Czech Republic, is known for many things. But one aspect of its history is often overlooked – it was a major center of the occult and the dark arts in the 16th century. Evidence for this side of Prague emerged with the discovery in 2002 of an old building that appears to have been an alchemy lab – the Speculum Alchemiae.

Discovering the Speculum Alchemiae

In 2002, the city of Prague was struck by a devastating flood which left up to 30,000 people homeless and at least 16 people dead. During the clean up after the flooding, a house was found in the Jewish quarter containing numerous underground laboratory facilities dating to the 16th century. Further examination of the building led those who found it to believe that it was an alchemical laboratory.

The discovery consisted of alchemical workshops with equipment and an underground network of tunnels that connected three important sites in Prague – the Old Town Hall, the Barracks, and Prague Castle.

The house is now the site of the alchemical museum, Speculum Alchemiae.

‘Alchemy.’ The Speculum Alchemiae museum in Prague shows the city’s occult side.

‘Alchemy.’ The Speculum Alchemiae museum in Prague shows the city’s occult side. Source: CC0

In the 16th century, Prague was the domain of the Holy Roman Emperor Rudolf II (1552-1612). Rudolf II is known for having been a major patron of the arts and sciences. He was named Holy Roman Emperor in 1576 and came to rule in the city of Prague in 1583. Until his death in 1612, Rudolf II helped make Prague into one of the leading centers of scientific research and artistic production in Europe. He hosted some of the most important scientists, philosophers, and artists on the continent at that time. Some prominent scientists who worked in Prague under his patronage were the astronomers Tycho Brahe (1546-1601) and Johannes Kepler (1571-1630).

Portrait of Holy Roman Emperor Rudolf II (1590s) by Hans von Aachen.

Portrait of Holy Roman Emperor Rudolf II (1590s) by Hans von Aachen. (Public Domain)

In addition to the emperor’s interest in science, he also appears to have taken an interest in the occult. Rudolf II was a patron of alchemists and interacted with well-known mage-type figures such as John Dee and Edward Kelley. This 16th century laboratory appears to have been a result of the emperor’s interest in arcane things that belong to the hidden wisdom of past ages.

Rudolf II: Science Enthusiast and Occultist?

Today, there is a clear separation between what is considered science and what is considered mysticism and magic. Alchemy, astrology, and similar disciplines are considered pseudoscience by scientists today. In the 16th and 17th centuries, however, there appears to have been less separation between science and mysticism. Many figures considered to be great scientists today were also fascinated by the occult. Johannes Kepler, for example, was also an astrologer. Isaac Newton, in addition to making revolutionary contributions to the field of classical mechanics, also spent much of his life studying alchemy. Robert Boyle, the father of modern chemistry, was also heavily influenced in his thinking by earlier alchemists.

On the other hand, John Dee, well-known for being an alchemist and mystic, was also a brilliant mathematician and astronomer who also did work in navigation. These are all pursuits that would be considered legitimate science today.

Portrait of John Dee

Portrait of John Dee. (Public Domain)

As a result, it is possible that Rudolf II did not see a major distinction between his interest in astronomy and mathematics on one hand and his support for alchemy, astrology, and the occult on the other. He, like many intellectuals at the time, may have seen them as mundane and fantastic sides of the same spectrum. They were all scientific pursuits.

Reason for Secrecy

Although alchemy and similar disciplines were considered legitimate scientific disciplines at the time, there was still some risk in practicing them. It is interesting that Rudolf II chose to build this alchemical laboratory facility in the Jewish quarter. It is possible that the reason for this was that, in some ways, Judaism was friendlier at the time to the occult sciences than Christianity. Thus, constructing it there would have aroused less suspicion.

Part of the Speculum Alchemiae.

Part of the Speculum Alchemiae. (Steven Feather/CC BY NC SA 2.0)

Legacy of Alchemy

Alchemy is no longer accepted as a scientific way of looking at nature, but there is growing historical evidence that early alchemists did make useful contributions to science and laid the groundwork for the foundation of later fields such as physics and chemistry. Although alchemists did not always understand the results of their experiments, alchemical experiments did occasionally produce real and interesting findings.

One example is the philosopher’s tree - the result of an alchemical experiment that produced a tree-like structure of gold. A chemist and science historian at John Hopkins University, Lawrence Principe, has used alchemical texts and notebooks to repeat the experiment and has been able to produce the philosopher’s tree.

Well-developed Diana's tree (Philosopher’s Tree) grown up over copper rod from silver/mercury amalgam placed in 0.1 M solution of silver nitrate - reaction time 2 hrs.

Well-developed Diana's tree (Philosopher’s Tree) grown up over copper rod from silver/mercury amalgam placed in 0.1 M solution of silver nitrate - reaction time 2 hrs. (CC BY SA 4.0)

Alchemists did not succeed in transmuting base metals into gold, but they may have been onto something even if they didn’t realize it. It is possible that alchemy was a protoscience in the 16th century, a precursor to a full-fledged scientific field, rather than a pseudoscience. This makes the alchemy lab a precursor to a scientific laboratory. Instead of being a dead end, the work of medieval alchemists paved the way for the work of modern chemists.

Top Image: Inside the alchemy laboratory of the Speculum Alchemiae museum. (alxmjo/CC BY NC ND 2.0)

By Caleb Strom


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Speculum Alchemiae. (2018) “Speculum Alchemiae About page.” Speculum Alchemiae. Available at:

Wisse, Jacob. (2013) “Prague during the Rule of Rudolf II (1583–1612).” In Heilbrunn Timeline of Art History. The Metropolitan Museum of Art. Available at:



you are correct. many of those prominent figures in science, who practiced alchemy were also member of secret fraternities like the Rosicrucian and the Freemasons, for whom the study of alchemy was about purifying the self using Hermetic Principles.

When people hear the word “alchemy” their thoughts immediately turn to changing base metals into gold. There was (is?) do much more to this science. Thank you for this article.

Caleb Strom's picture


Caleb Strom is currently a graduate student studying planetary science. He considers himself a writer, scientist, and all-around story teller. His interests include planetary geology, astrobiology, paleontology, archaeology, history, space archaeology, and SETI.

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