Heritage groups have called for the preservation of what looks like an underground vaulted reservoir discovered underneath a historic Sliema home being turned into a boutique hotel.

The underground vaulted reservoir discovered underneath a historic Sliema home.

The Sliema Heritage Society was contacted after Times of Malta received photographs from concerned residents over what could be a historical discovery.

Building industry sources said the Planning Authority permit usually contained a standard condition that the Superintendence of Cultural Heritage must be informed of any historical finds.

The Cloisters, a Grade 2 scheduled building in Mrabat Street, is being converted into a 29-bedroom boutique hotel, with a stepped block of 27 apartments and maisonettes overshadowing it at its rear by replacing the garden with a seven-storey development.

The permit was granted to Bilom Group in February last year. The project will see the addition of a storey to the facade and the obliteration of the extensive back garden, making way for an apartment block rising 21 metres above the building, which is within the urban conservation area.

The application had been recommended for approval by the Planning Directorate and the Superintendence of Cultural Heritage had raised no objections.

The heritage watchdog, which visited the site and met the architect to discuss details of the project, noted that the Cloisters building had architectural and historic value and lay close to several other scheduled properties.

Call for immediate action to ensure its preservation

It also noted that the project would involve the restoration of the historic building and the demolition of non-scheduled parts of the property.

Alterations on scheduled buildings can only be carried out if they are sensitive and do not detract from the character or architectural homogeneity of the site.

A spokesman for the Sliema Heritage Society, which had objected to the development, said the vaulted reservoir was something that should be preserved.

He called on the Superintendence of Cultural Heritage to take immediate action to ensure its preservation and inclusion in the project.

The approved plans includes the creation of underlying garages having 55 parking spaces. With the discovery of the reservoir, the garages might need to be scrapped or changed, the spokesman said.

The Superintendence for Cultural Heritage did not reply to questions on whether it was aware of the find.