Fort Zverev, located on the shores of the Baltic Sea in northern Kronstadt, lies in complete ruins today. One of the several forts of Kronstadt, Fort Zverev was built in the 1860s by the engineer Konstantin Zverev, after which the fort is named, in order to strengthen the northern fairway of Gulf of Finland. The fort had a mushroom shape with curved ceiling, a new design different from all Konstantin Zverev had built before. In fact, it was Zverev who for the first time in Russia had successfully applied asphalt as a building material, covering the floors with natural asphalt solution.

At the beginning of the 20th century the fort was converted into a warehouse of sea mines and ammunition dump, and continued to remain on duty long after World War II ended, as a site for military training and practical shooting.

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In 1970, a devastating fire broke out on Fort Zverev that raged for several weeks. When the fire finally subsided and the fort cooled down enough to enter, the basement was completely unrecognizable. The inferno was so hot that it literally melted the bricks above which dripped down like stalactites. It’s not known what kind of material fueled the fire but from the nature of the damage, it was evident that it was something that burned intensely hot.

In any normal household fire, even a very strong brick does not melt. This requires a long enough temperature not less than 1,800 degrees centigrade. For comparison, a large gasoline fire will produce temperature of about 1,100 degrees. Some speculate that the Russians were testing a new kind of weapon – possibly a high phosphorus containing compound similar to napalm that burned at temperatures in excess of 2,000 degrees centigrade.

According to another version, the fort was a cesspool of lubricants and decommissioned ammunition, bilge water and waste from ships that was accidently set fire by careless tourists. The truth will never be known.

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At places the melted layer fell off, exposing the dead burned brick. Photo credit

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Sources: boat.ucoz.ru / Dmitrij badyaev / Atlasobscura / Oddity Central