The common phrase “written in stone” refers to something relatively permanent. Prague officials didn’t take this into account when they decided in late 2013 to launch a city guide for smart phone by placing a QR code made of black-and-white paving stones right in front of the main entrance to City Hall on Mariánské náměstí.

While the message in stone has been long-lived, the city guide app was fairly fleeting. Since sometime in 2019, the stone QR code has been instead redirecting people to an internet prank. City Hall is either unaware of the issue or does not have the will to file all the Kafkaesque paperwork required to change the sidewalk in the protected monument zone.

The QR code directs the user’s phone to go to a web link — mhmp.eu/qr — which originally took you to an app called Praha chytře (Clever Prague), available free for Android and iOS.

At the time it was launched, QR codes were still a bit of a novelty. “Head with a smart phone to the sign in front of the entrance at Mariánské náměstí and enjoy the city’s life and fun,” City Hall announced back on the halcyon day of December 12, 2013.

“The mysterious symbol at the steps of City Hall will help you download a useful app — Praha chytře. It … serves as a complete guide to life in the city: it offers traffic cameras, news from Prague, a calendar of cultural and sports events, contacts for City Hall and the city districts,” they said optimistically.

“Since it is connected to the Internet, it regularly updates the selected data and stores it on your mobile phone. They can then be displayed even without a connection,” they added, awed by the power of the digital realm.

But Clever Prague was short-lived, as much of the information was readily available without having to use a cumbersome app. The idea wasn’t so clever after all.

The related Praha chytře website is now a dead link, and even the mobile app shop called Praha! seems to be a distant memory. The city still offers some apps including Moje Praha (My Prague), which has 2.9 star rating as the information on it, according to reviews, is out of date.

For several years the QR code, like the app website, simply didn’t function. But never say never. Eventually it rolled back to life. People who didn’t give up on scanning it eventually got a reward.

If you want the full Praha chytře experience, scan the QR image now or enter the related link. Spoilers lie ahead.

Dead links are found treasures for some people. They can be bought up rather cheaply and used for nefarious purposes. Many a politician has grown to regret letting an opponent get their hands on an expired campaign web domain, and having it turned against them. And getting the URL back is a complicated and often unsuccessful process.

Whoever found the dead QR code link wasn’t as evil as that. The link, for example, doesn’t give you directions to tourist info for Brno or České Budějovice, or a timetable for buses to Kladno.

The revived link now directs users to Ricky Astley’s classic 1987 rock video “Never Gonna Give You Up.” In internet parlance, that is called a “rickroll.” The official version of the video has over 651 million views, and most of those come from people being tricked or “rickrolled” into going there. Other versions, since deleted for copyright infringement, together had billions of views.

The song was big hit when it first came out, but also just as widely hated. When the practice of using shortened URLs, which can hide the real destination, became common, directing people to “Never Gonna Give You Up” became the punchline to a practical joke. This culminated in widespread rickrolling on April Fools Day 2008, the peak time for this prank.

The City Hall QR code has been discussed on Reddit several times. “Someone probably found out the link was broken and bought the URL in order to redirect it to RickRoll people in the future. This is top tier r/madlads material lol,” one Redditor speculated. “Nice. Well played, well played,” said another.

And the joke will carry on for generations, if City Hall doesn’t ever fix the sidewalk. “That’ll confuse the hell out of future archaeologists,” one person speculated.