AILSA CHANG, HOST:
In Prague's historic Old Town Square, you will find an intricate, 600-year-old piece of machinery, the Orloj.
(SOUNDBITE OF CLOCK CHIMING)
SACHA PFEIFFER, HOST:
It's a colorful medieval clock, and it's one of the most famous sights in Prague. It's in every tourist guide, and there's always a crowd watching it.
THOMAS MCENCHROE: You have all these sort of little puppets that move and dance. So it is a very sort of popular attraction for tourists who come here.
PFEIFFER: That's Prague Radio International's Thomas McEnchroe.
MCENCHROE: It's a sort of symbol of national pride as well.
CHANG: The Orloj has been repaired several times since it was built in 1410. The last major renovation cost the city $2.6 million, and it was finished in 2018. That's when art restorer Stanislav Jircik was commissioned to paint a replica of the clock's iconic rotating calendar plate.
MCENCHROE: Imagine it as a big circular sort of picture on which, you know, different months are sort of artistically depicted as images.
PFEIFFER: But four years after he finished it, a member of a local preservation group noticed something was off.
MCENCHROE: And he just noticed so many mistakes. The images are very different to the original.
PFEIFFER: There weren't major differences, just lots of little things.
CHANG: Like in the original, there is a black dog. But in Jircik's version, the dog is brown. Or a figure is painted older or with different hair. The more you look, the more changes you find.
MCENCHROE: The Czech Republic is in the news, and it's a bit embarrassing - isn't it? - on one hand. And on the other hand, it's just a sort of strange joke that nobody noticed this for four years.
PFEIFFER: Some people think Jircik was playing a prank on the city. Others think he painted his own friends into the piece.
MCENCHROE: But he has refused criticism, and he says that he was inspired by the original artist.
CHANG: For now, the new painting is still on display in the Old Town Square. But investigators from the Ministry of Culture are on the case, and surely they are working around the clock to solve it.
(SOUNDBITE OF HONEYMOAN SONG, "WE") Transcript provided by NPR, Copyright NPR.