Why did the dinosaurs cross the bridge? After two of the large, prehistoric creatures were spotted sauntering over the Thames this past Monday, much of London is searching for the answer to this riddle.

The dinos took their stroll around 4 pm on Monday, “leaving the capital’s tourist and office workers bemused,” writes the Evening Standard. Photos and video footage show the two carnivores easing on down the bridge’s pedestrian sidewalk, tiny arms swinging.

“It is not clear why the dinosaurs were on the bridge” the Southwark News reports—although several commenters suggested some kind of viral marketing campaign, possibly tied to an upcoming museum exhibit.

The most obvious answer to the riddle, of course, is that dinosaurs can do whatever the heck they want. Oh, and also, to get to the other side.

Every day, we track down a fleeting wonder—something amazing that’s only happening right now. Have a tip for us? Tell us about it! Send your temporary miracles to cara@atlasobscura.com.