Statement. Salamanca hides three famous search problems: a small carved frog on the Plateresque facade of the University, an astronaut added to the New Cathedral’s Puerta de Ramos in the 1992 restoration, and a legendary gold coin under one of the 300-plus shells of the Casa de las Conchas. We visited in September 2026 and solved two of them.
Some cities are museums. Salamanca is a problem set. Its golden stone facades are full of hidden things, and half the visitors in the old town are running search algorithms with their necks bent back. We ran three.
Where is the frog on the University of Salamanca facade?
On the Plateresque facade of the University’s historic building, among coats of arms, medallions, skulls and grotesques, sits a small carved frog. The University traces its origins to 1218, and spotting the frog has been a rite of passage for visitors for a very long time.
The naive method is linear search: scan the facade panel by panel until you hit the frog. Worst case, you check everything; average case, half. The facade is large, the frog is small and the sun is usually in your eyes. The smart method is what everyone actually does: look where other people are pointing. In computer science that is called consulting an oracle. In Salamanca it is called standing next to a tour group.
We found it. We won’t tell you exactly where. Some proofs are left as an exercise for the reader.
Where is the astronaut on Salamanca Cathedral?
The New Cathedral was begun in 1513 and consecrated in 1733. During the 1992 restoration of its Puerta de Ramos, the side portal facing the Plaza de Anaya, stonemason Miguel Romero carved a small astronaut into the stonework, following the old custom of leaving a sign of your own time when you restore a building. It sits on the left side of the portal as you face it, at mid height, and you can see it from the street for free.
This is anomaly detection: finding the element that does not fit the distribution. It should be easier than linear search, because the target is weird. In practice, a Gothic portal is already so weird that an astronaut blends in surprisingly well. We found this one too. Some websites present it as proof of ancient time travellers; the true story, a stonemason with a sense of humour and a date, is better.
Is there really a gold coin under a shell of the Casa de las Conchas?
The Casa de las Conchas, built around the turn of the sixteenth century and now Salamanca’s public library, carries more than 300 stone scallop shells, the emblem of the Order of Santiago. Local legend says a gold coin is hidden under one of them.
Assume the coin is equally likely to be under any shell (a uniform prior) and that you lift shells one by one without repeating. With n shells, the expected number of lifts is (n + 1)/2. For 300 shells, that is 150.5. Plus one conversation with the local police, which the formula does not include.
Professional searchers use something smarter: Bayesian search theory, which updates the probability of every location after each failed look. It helped locate the lost submarine USS Scorpion in 1968 and the wreck of Air France 447 in 2011. As far as we know, nobody has applied it to Salamanca’s shells. We recommend keeping it that way. The whole walk is in the Salamanca proof.
Conclusion: two out of three
Salamanca rewards the patient searcher: a frog, an astronaut and a legend with a well-defined expected value. Our score was two out of three. The coin stays under its shell, where it belongs. The library, in any case, is the better treasure: free to enter, open long hours on weekdays, and full of books that are much easier to find than frogs.
Quick guide
- Frog: Plateresque facade of the University of Salamanca, historic building (Escuelas Mayores). Bring patience, or a tour group.
- Astronaut: Puerta de Ramos of the New Cathedral, facing the Plaza de Anaya, left side, mid height. Free to see from the street.
- Shells: Casa de las Conchas, Calle Compañía 2, opposite the Clerecía. The patio is free; check the library’s current hours on the Junta de Castilla y León website before you go.
Frequently asked questions
Where is the frog on the University of Salamanca facade?
It is carved among the decoration of the Plateresque facade of the University’s historic building. Finding it yourself is part of the tradition.
Where is the astronaut on Salamanca Cathedral?
On the Puerta de Ramos of the New Cathedral, the portal facing the Plaza de Anaya: on the left side as you face it, at mid height. It is visible from the street for free.
Why is there an astronaut on Salamanca Cathedral?
Stonemason Miguel Romero carved it during the 1992 restoration of the Puerta de Ramos, following the stonemasons’ custom of leaving a sign of their own time when restoring a historic building.
How many shells does the Casa de las Conchas have?
More than 300 stone scallop shells, the emblem of the Order of Santiago. The building now houses Salamanca’s public library.