A huge kaleidoscope is being built on Rijeka's Korzo, the main pedestrian thoroughfare which runs through the heart of the city centre.
The giant optical instrument is just one of many interactive and installation aspects of Rijeka European Capital of Culture 2020.
As the photos show, the kaleidoscope straddles much of the street and has ample room for many people to walk beneath it.
The kaleidoscope's construction will easily be completed in time for the Inauguration of Rijeka as European Capital of Culture 2020 on Saturday 1 February.
As an optical instrument, the kaleidoscope is over 200 years old and is credited as having been invented in 1815.