Dugi otok

Circles under the sea

31 December 2021.

Written by Matija Čaić

Long Island, do not mistake it with the one in New York City, is the largest and most remote island of the Zadar archipelago. The name was given by being approximately ten times longer than it is wider (44.5 km in length versus just 4.8 kilometers in average width). There is much to see on it, from Roman ruins to Telaščica Nature Park. But the most interesting thing for true researchers is hidden below the surface.


Circles in the grain have already become so common in promoting life outside the Earth that the aliens no longer know what new things to do, so they started to do a real masterpieces in the grain .
In Croatia, however, they have decided to do something more radical that is unique in the world.

They decided to put the circles under the sea surface. Since Croatia is a country with a strong maritime tradition and Adriatic tourism that is one of the best in the world, it seems that our alien partners have chosen to use it.

Jokes aside, the fact is that along the coast of Dugi otok there are 28 regular circles of 50 meters wide which for now no one has managed to figure out how they came about. What makes the researchers particularly impressed is their uniformity. All are of identical dimensions and looks, are about one hundred meters from the uninhabited coast of the island, very close to each other, located at a depth of 20 meters, and apart from the coast of the Dugi otok, can be seen along the coast of the island of the Unije and several other smaller islands

They were first discovered in 2013. by biologist Mosor Prvan recording the shore of the island from the air.

The circles are made in the sea-grass of the Latin name Posidonia oceanica, which is an endemic to the Mediterranean. Those who dived deep enough to see them describe them “as if somebody pulled the grass from the bottom with a corkscrew” and after that, posidonia never again appeared in that place.

There have been many attempts to explain their occurrence. Even the well-respected Discovery Channel tried to discover their secret. Unsuccessful.

Possible theories

The theory that most people believe in is that the circles are made by explosive. Most likely poachers who hunt fish with dynamite or army. This theory was first put up by biologist Donat Petricioli, and also confirmed by an unknown man claiming to be present when the then Yugoslav National Army checked the stability of the ground for building a military base on Velebit Mountain in the late eighties of the twentieth century. Since it was a military secret, his story could not be confirmed.

However, explosives experts are reluctant to support this theory as they think the circles are too regular to be the result of something as unsophisticated as an explosive.

In Denmark, the circles under the sea have also been discovered and were result of some toxic substance destroying the grass, but they are not as close to as regular as this Croatian, so that theory has also been rejected.

Much more interesting is the second theory of their emergence. Geologist and ufologist Stjepan Zvonarić stated that the circles must be at least 20,000 years old and that they are in fact the remains of an alien base in which they have landed during exploratory expeditions.


The undeniable facts are the following. The circles are all of the same size and shape, they are almost perfect circle, equally far from the shore and from each other, all of which point to the precise work of human or some other hand.

Hum – the smallest city in the world


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