Flimkien Għal Ambjent Aħjar yesterday expressed concern about development application PA 00167/08 dealing with an extension at St John's Co-Cathedral Museum in Valletta.
The proposed project will include the construction of a three-storey high building on the courtyard along Merchants Street to provide additional space and a canteen at roof level.
According to the development application, the façade of the co-cathedral along Merchants Street will be altered by the proposed structure that will stand above the graves of the Knights of the Order.
A second application, PA 00168/08, proposes to extend St John's Co-Cathedral Museum by excavating chambers below St John's Street, connecting them to existing underground water reservoirs, and constructing a vertical lift through all the floors, apart from alterations.
The two water cisterns there are among the earliest in Valletta, thought to have been built on the insistence of Francesco Laparelli and should therefore be preserved intact as evidence of the advanced engineering techniques and the foresight of the Order in assuring Valletta's water supply, the FAA said.
"This underground exhibition space is intended to house the Gobelins tapestries. However, in addition to the problems of creating access, this would require a considerable air and humidity control installation, which will cause further damage to the vaulted cisterns.
"It is felt that the potential risks posed by exhibiting priceless tapestries in underground chambers, as well as the inevitable damage to part of the most important monument that Malta possesses, are totally unacceptable," the NGO said.
Furthermore, excavations at St John's Square to provide more chambers might not only affect the cathedral's foundations but also destroy the remains of previous knights' period structures, it added.
The FAA insisted that such a historical and long-established urban environment that has long been enjoyed by Valletta residents and visitors should not be destroyed, disrupting the community by depriving it of trees that are essential for shade and help to remove pollutants from the air.
In its reaction, the St John's Co-Cathedral Foundation said it would never risk any damage to the Co-Cathedral which is a world treasure.