The Baron Empain Palace, a Heliopolis landmark, is set to open its doors to the public in October, following the completion of its first-ever restoration.

Sitting empty in the upscale neighbourhood of Cairo for the last several decades, the unusual building has long sparked rumours of ghosts and satanic rituals.

But the restoration of the 1911 mansion, which was built by Belgian industrialist and founder of Heliopolis Baron Edouard Louis Joseph Empain, has sparked debate in recent days.

Controversy first stirred when pictures of the palace emerged showing the outer façade in a burnt sienna colour, in contrast to its previous light beige.  

The Facebook page Egyptian Historians on Facebook responded angrily, describing the restoration, which is being carried out by the armed forces’ engineering corps under the antiquities ministry, as “a defamation.”

"Please respect us and admit the mistake you've made. You continue to literally destroy our antiquities and you have led us to wish that you don't restore anything ever again," wrote the page owners in a post.

By contrast, the Historic Cairo Facebook page shared a post defending the restoration work and describing the burnt sienna colour as “historically accurate.”

A general view of the restoration work at the Baron Empain Palace, "Qasr el Baron" or The Hindu Palace, built in the 20th century by a Belgian industrialist Edouard Louis Joseph, also known as Baron Empain, in the Cairo's suburb Heliopolis, Egypt August 18, 2019. (REUTERS)

Following a tug-of-war on social media around the renovation, the antiquities ministry finally responded with a defence of the EGP 100 million project.

The ministry said that the colours of the restored façade are “original,” stressing that those entrusted with the project have carried out all necessary procedures, including tests and photographical and architectural documentation of damage, to make an appropriate plan for the restoration.

The tests showed that the burnt sienna colour was in fact authentic, the ministry added.

The ministry said it had determined the original colour through historical documents, citing the book Le roman d'Héliopolis by historian Amelie D. Arschot, who writes that the building was in burnt sienna and white and was inspired by 12th century temples in northern India.

Mostafa Waziri, secretary-general of the Supreme Council of Antiquities, said around 90 percent of construction work on the renovation has been completed so far, including the structural consolidation of the roofs and a restoration of the facades' adorned elements.

He agreed that the sandy colour of the exterior that is so familiar to passers-by was due to erosion, which altered the original colour of the palace.

"It was not reasonable to leave the palace [as it is] without restoring its original colour," he said.

Minister of Antiquities Khaled El-Enany has also defended the removal of an outer fence around the palace, saying it was only installed 14 years ago.

A new fence has been added, and El-Enany stressed that a second, original fence will not be removed.

This is not the first time that the palace has been the subject of controversy.

In June, Egyptian officials denied reports that the palace had been put up for sale, stressing a pledge to preserve all of the country’s historic monuments and cultural heritage.

The current restoration of the palace is part of Egypt’s plan to execute EGP 2.5 billion in antiquities projects in the near future, with EGP 1.47 billion to be spent by December 2019 and EGP 1 billion in 2020.

After restoration, the palace will feature a historic exhibition on the history of Heliopolis, as well as a visitor services area.

Officials hope that visitors will be curious about the mysterious landmark, and have stressed that ticket prices won’t be too steep for Egyptians.

Also known as Le Palais Hindou, the building was designed by French architect Alexandre Marcel and decorated by Georges-Louis Claude.

Empain came to Egypt in 1904 with his company, with hopes of building a railway linking Mansoura to Matariya. Although his company ultimately lost the railway contract, the entrepreneur nevertheless stayed on in Egypt, and was responsible for creating what was then the new city of Heliopolis.

A previous attempt to restore the palace in 2010 stalled after it lost its budget following the 2011 revolution.