A mysterious metal monolith appeared in the Netherlands after similar objects were found in the U.S., Romania and Britain, an official said.
Hikers found the object on private land near a nature reserve in a northern province, a spokesman for the Dutch Forestry Commission said.
He added, “We know that it was probably placed this weekend because some hikers who were walking there found it, but we don’t know it got there.”
Rangers went to check out the object and were still hunting for clues to its provenance.
A similar-looking structure appeared in the Utah desert late last month, then two others cropped up in southern California and Romania days later. Another appeared on a beach on the Isle of Wight off the south coast of England soon after.
Photos in Dutch media showed the object with a dull silver-colored surface, standing next to a marshy pool on frosty ground.
The appearance of the Utah object sparked wild rumors of alien visitations.