Concrete structures forming part of the army’s maritime base upgrade near the Excelsior hotel are not a threat to Valletta’s World Heritage status, according to Unesco.

The UN agency for education and culture told Times of Malta the base below the Floriana bastions fell outside the World Heritage site boundary.

The building of two vertical concrete structures on the waterfront has caused a stir because they overshadow the bastions behind them. Environmentalists have questioned whether they could threaten Valletta’s status. Similar concerns were raised in the past about the Excelsior, luxury apartment blocks at Tigné and Renzo Piano’s City Gate plans.

But Unesco’s Petya Totcharova, chief of the Europe and North America Unit at the World Heritage Centre, told this newspaper that based on the official maps of the World Heritage site, it appeared the structures did not fall within the boundaries of Valletta or its immediate vicinity.

“Therefore they do not seem to represent a threat for the World Heritage status of the property.”

Ms Totcharova’s comments were echoed by Superintendent of Cultural Heritage Anthony Pace, who said the development fell outside the buffer zone of the Unesco World Heritage site.

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