Explore a Renaissance Alchemy Lab

If you ever find yourself in Prague, here's a fascinating restoration project that you can visit. In 2002 a homeowner found that one of his basement walls had collapsed after heavy rains hit the city. Behind the wall he found a secret passage leading into the remains of an actual alchemy lab dating back to the European Renaissance. After ten years of restoration based on period drawings and engravings, the lab is now called Speculum Alchemiae and is open to the general public. This article provides an account of visiting the site written by a modern chemist.

Speculum Alchemiae offers thirty minute tours of the subterranean laboratories. Luckily, when I visited, the tour group consisted of just my travel partner and I, and the very knowledgeable tour guide. It didn’t require much imagination to be transported back to times gone by; the quest for the philosopher’s stone, elixir of eternal youth and transmutation (turning metals into gold). The whole of foggy, gothic Prague lends itself to this transportation. Speculum Alchemiae is really just the cherry on the cake.

The laboratory is believed to have been built at the behest of Emperor Rudolf II – Holy Roman Emperor between 1576 to 1612, and a great alchemy devotee. Whilst living in Prague he encouraged Europe’s best alchemists to his court; men such as Edward Kelley, John Dee, Tycho de Brahe and Rabbi Loew. He is even known to have performed some alchemy experiments himself. The secret passages connect the laboratories to Prague Castle, the Old Town Hall and Barracks – allowing alchemists to travel unseen between the four locations.


The history is fascinating, but as a chemist I was just as drawn to the actual workings of the laboratory. There are three main rooms. The first is a drying room, where plants were stored and dried, to be used in elixirs. The second is where most of the magic happened; with apparatus for plant distillation and elixir blending, and a transmutation oven. The third is a glass-blowing room; the alchemists made their own glass apparatus in order to be self-sufficient and avoid discovery. Oven exhaust was funneled through the house and out of its chimneys, as gases rising from under the streets would have been another sure route to discovery.

Edward Kelley is known to have conducted alchemical experiments for Rudolf II, so it's possible that he worked in this very laboratory centuries ago. Unfortunately for my off-the-cuff speculations about actually transmuting mercury into gold using radioactive elements, nothing of the sort was found in the laboratory. It may very well be that alchemists never experimented with radioactive materials, as doing so would have been extremely dangerous with the technology of the time.

However, it appears that the place was used for concocting herbal elixirs that could very well have been more effective than the raw herbs from which they were derived, which likely accounts for alchemy's association with medicine and healing. Work with "plant stones" of this sort could be thought of as the original version of the processes still used today to extract specific drugs from the plants that produce them. There are known alchemical procedures, for example, for extracting both polar salts and non-polar alkaloids from dried herbs, and the same methods were employed by early chemists.