Speculum Alchemiae – Prague’s Hidden Alchemical Laboratory

photography by: Sinéad Browne

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Famous as the “City of a Hundred Spires”, Prague is renowned for its gold-tinted architecture and cultural attractions. While the historic centre teems with tourists, a hidden part of the city often goes unnoticed – a relic of the occult and the Dark Arts practised here in the 16th century. Unveiled by chance following a devastating flood in 2002, the Speculum Alchemiae museum allows visitors to enter the world of an alchemist’s laboratory, replete with potions, elixirs and passageways kept secret for centuries.

History and Discovery

Dating back to 900AD, the museum site is one of the oldest dwellings in the city and the current building survived both the French Fire of 1689 and the destruction of most of the Jewish ghetto in the early 20th century. The links to alchemy were only uncovered as recently as 2002, when the Vltava River burst its banks in the worst flood ever recorded in the city.


A tiny square in front of the house collapsed under the extensive volume of water and revealed a previously-unknown series of underground rooms, covered with mud and detritus. The owner spent years clearing out the basement, uncovering preserved artefacts and sealed-off alcoves that contained alchemy texts and bottles of potions, slowly unveiling the subterranean site’s provenance as a 16th century alchemists’ laboratory.

Alchemy in 16th Century Prague

In medieval times, famine, plague and sudden death were a powerful trifecta of daily dangers. Alchemy seemed to offer a solution, aiming to transmute base metals into gold, cure diseases and achieve the ultimate goal of immortality.


These objectives, though they appear somewhat bombastic today, fascinated many esteemed analysts, including polymath Isaac Newton, chemist Robert Boyle and astronomer Johannes Kepler. Though often dismissed as a pseudoscience now, the lines between mysticism and mathematics were far more blurred in the Middle Ages and the byproducts of the work carried out in 16th century workshops helped to pave the way for present-day modern laboratories.


A staunch believer in the power of this esoteric chemistry, Holy Roman Emperor Rudolph II brought his court to Prague in 1583 and invited famous alchemists such as Edward Kelley and John Dee to the city to conduct their experiments. The Catholic church disapproved of alchemy and so the laboratory was buried underneath the unassuming house at 1 Haštalská Street, connected to Prague Castle via a hidden tunnel.


Believing that the remedies helped to treat his fits of severe depression, the emperor’s daily doses included an elixir of youth comprising 77 herbs and alcohol, and an elixir of love for both him and his mistress. Whether due to the potions or a powerful placebo effect, he lived to be 69 years old and his unwavering support of the arts and sciences helped to transform Prague into a leading centre of research and artistic production in Europe.

The Museum

Following years of painstaking exploration and reconstruction, the catacombs were transformed into the Speculum Alchemiae (“Mirror of Alchemy”) museum. The name references a 15th century manuscript describing the creation of a medicinal elixir, a copy of which is on display.


Elaborating on this theme, the museum entrance is filled with coloured bottles containing remedies for sale that have been recreated by Benedictine monks using as much of the original recipes as possible – while alcohol is still used, opium is not.


From the shop, a set of stairs leads down to the “office”, a room dominated by a large bookcase, stuffed crocodiles that were considered to be magical guardians and the ubiquitous glass bottles of liquids, one of which is said to be a preserved original potion.


Energy from the four elements is focused to the basement by a curious chandelier hanging from the ceiling, featuring images of the prophet Moses with horns. This unusual depiction arose from a translation of the bible where the Hebrew words for “horned” and “emitting rays” may have gotten confused.


The bookcase conceals a secret passageway to three downstairs rooms: an experimental workshop, a glass-blowing studio and a drying room for herbs.  The low-ceilinged rooms are adorned with replicas of the scientific apparatus that were used at the time, amongst them clay pots, beakers and flasks of all shapes and sizes.


Despite these rooms being underwater for so long, hidden alcoves successfully preserved Latin texts because they were so carefully sealed. As well as the secret tunnel to the castle, there are (now inaccessible) passageways leading to the Old Town and the barracks, possible escape routes for the alchemists if their work was discovered by those who considered it to be heresy.


It is also believed that there may be other rooms even deeper underground, but excavating these would not be possible at the current water levels.


While the tour is short (about 30 minutes) and the plethora of potions, skulls and other occult symbols may feel a little gimmicky, the guides are well-informed and entertaining, giving visitors an insight into a lesser-known aspect of life in medieval Prague.

Getting There

Located at 1 Haštalská Street, the museum is open every day from 10am to 6pm. It is a short walk from the Old Town or from the Náměstí Republiky stop on metro line B (yellow line). The underground part of the museum is accessible by guided tour only.  Tours cost Kč 200 (€10) per adult and payment is cash only, in either euro or Czech koruna.