In order to protect new structures from harm, or to bring good luck, some European cultures used to conceal the bodies of cats on the premises, inside hollow walls, under floorboards, or in attics. The two shown here were discovered in the Stag Inn in Hastings, East Sussex, which was built in the 16th century. Sometimes the animals have been posed with prey, as here, but happily it appears that they weren’t walled in while still alive; in some cases they’ve been found in places that they couldn’t possibly have reached on their own.

I wonder if this practice explains a couple other instances that I’ve come across over the years. The Guildhall Library has some further examples.

Tomorrow’s date will be written as an eight-digit palindrome around the world, the first time this has happened in 900 years.

The coincidence is rare because countries use differing conventions. February 2, 2020, is a palindrome whether expressed as day/month/year (02/02/2020), month/day/year (02/02/2020), or year/month/day (2020/02/02).

This happened last on November 11, 1111, and it won’t happen again until March 3, 3030.

02/01/2020 UPDATE: A number of readers have pointed out that 12/12/2121 works fine too, and it’s barely more than a century away.

Numbers 23 and 24 Leinster Gardens, London, are not the terraced houses they appear to be. Their façades match their neighbors’, with columned porches and windows and balustraded balconies, but the doors have no knobs or letter boxes.

In fact the whole expanse is false, only a façade 5 feet thick. Behind it is a section of uncovered railway track. When a tube line was built through the neighborhood in 1863, the steam engines that hauled the trains needed a section of uncovered track to let off smoke and steam. To preserve appearances for the surrounding residents, the railway company built these frontages, and they remain to this day.

Writes Stuart Barton in Monumental Follies, “It is unfortunate that more sham facades like this are not built to conceal some of the eye-sores that scar our cities today.”

There’s not much to say about this, but it’s wonderfully picturesque: Standing near the village of Plougrescant on the coast of Brittany is Castel Meur, “the house between the rocks.”

Constructed in 1861, it’s situated between granite rocks to protect it from storms.

01/28/2020 UPDATES:

Casa do Penedo, in northern Portugal, has boulders for its foundation, walls, and ceiling. (Thanks, Rui.)

Wickhams department store planned an imposing new edifice in London’s East End in 1923, but the Spiegelhalter family refused to sell its jewelry shop, so the Wickhams facade had to be built “around” it. The “Spiegelhalter gap” was never closed — the department store closed in the 1960s, while the jewelers’ held out until 1982. (Thanks, Nick.)

St. Govan’s Chapel in Pembrokeshire, Wales, is built into the side of a limestone cliff — visitors must climb down a flight of 52 stairs to reach it. (Thanks, Chris.)

In 1993, Tennessee minister Horace Burgess was praying when God told him, “If you build a treehouse, I’ll see that you never run out of material.” He set to work and spent the next 12 years building a house 97 feet tall, unofficially the largest in the world.

The house was closed in 2012 because it didn’t follow building and fire safety codes, and last October it burned to the ground. Burgess told the New York Times that in some ways this was a relief. Though it had been important to him for decades, “It’s always been a pain,” he said.

Austin game developer Frank Force has won the Neural Correlate Society’s 2019 Best Illusion of the Year Contest with this “dual axis illusion”:

“This spinning shape appears to defy logic by rotating around both the horizontal and vertical axis at the same time! To make things even more confusing, the direction of rotation is also ambiguous. Some visual cues in the video will help viewers change their perception.”

The top 10 finalists are here.

12/18/2019 UPDATE: Good heavens, people are making these things. Five years ago Bill Gosper created the Lissajoke ambiguous roller, which rolls in a perplexing way:

And reader Joe Kisenwether has rendered Force’s illusion in reality — here the shape on the left spins about a horizontal axis while the one on the right spins about the vertical one:

The same thing rendered more slowly:

(Thanks, Joe.)