Beneath what remains of the 12th-century Al-Hadba minaret, builders work on a project to restore Mosul's Old City, reduced to rubble during Iraq's battle to retake the city from jihadists.

Mosques, churches and century-old houses are being brought back to life in the northern metropolis, which the Islamic State (ISIS) group seized as its stronghold before being pushed out in mid-2017.

"Al-Hadba is the icon of Mosul, the symbol of the city," said Omar Taqa, a supervising engineer with UNESCO, the United Nations heritage body which has launched several projects to restore the city's landmarks.

The minaret was featured on Iraqi 10,000-dinar banknotes before the jihadists flew their black flag from the top of its 45-metre spire.

ISIS chief Abu Bakr al-Baghdadi made his only confirmed public appearance in July 2014 at the Al-Nuri mosque, where he declared the establishment of a "caliphate".

Three years later, Iraq's army and a US-led international coalition had forced the jihadists out of Iraq's second city. The Al-Nuri mosque and the adjacent leaning minaret, nicknamed Al-Hadba or the "hunchback," were destroyed in June 2017 during the battle to take back the city.

Iraqi authorities had accused ISIS of planting explosives there before their withdrawal.

"We found 11 mines there, ready to be activated," said Taqa. "Some were hidden inside walls."

Only the central area of the mosque remains, its dome propped up on arches supported by wooden wedges. Atop the columns of grey marble, traces of blue enhance the adjoining capitals.

As for Al-Hadba, only its base remains standing, protected by a sheet of tarpaulin. Having removed about 5,600 tonnes of rubble, the reconstruction of the minaret begins in mid-March, retaining its tilt, while work on the mosque is due to begin in the summer.

By the end of 2023, the site should be ready.

"Revive the Spirit of Mosul"

While awaiting reconstruction, the more fragile parts of the structures are kept in a warehouse.

These include fragments of the Mihrab, a niche indicating the direction of Mecca for worshippers, as well as pieces of the Minbar, from where the sermon is delivered and Baghdadi made his declaration in 2014.

Around 45,000 terracotta bricks from the original minaret, about a third of those that made up the structure, are lined up on shelves to be reused, Taqa explained.

Discoveries are still being made at the site, where in January a 12th-century prayer room was found under the mosque.

The UN agency raised $110 million for its "Revive the Spirit of Mosul" initiative, largely financed by the United Arab Emirates and the European Union.

Al-Tahira and Our Lady of the Hour churches are also set to be restored, as well as about 120 houses and the local school in the Old City.

Local contractors are handling the construction which has created 3,100 jobs. About half of those are for young people who have been trained in heritage and building restoration, UNESCO said.