PALMYRA, SYRIA (AFP) - Syria's ancient city of Palmyra was recaptured by government forces from the Islamic State in Iraq and Syria (ISIS) militant group over the weekend. Here are five things to know about Palmyra:

It is a Unesco world heritage site

The archaeological treasure was designated a world heritage site by the UN cultural agency Unesco in 1980. It was seized by ISIS in May last year and the militants sent shock waves around the world during the autumn with a systematic campaign of destruction of the city's monuments.

Before Syria's devastating civil war erupted in 2011, the city attracted more than 150,000 tourists a year.

Rose to prominence during the Roman empire

Although the precise date of its founding is unknown, Palmyra's name is referred to on a tablet dating from the 19th Century BC as a stopping point for caravans between the Mediterranean and the east.

It was during the Roman Empire - beginning in the First Century BC and lasting another 400 years - that the oasis city rose to prominence.

Despite being surrounded by desert, Palmyra developed into a wealthy metropolis thanks to the trade in spices, perfumes, silk and ivory from the east.

Palmyra means City of Palms

Known to Syrians as the "Pearl of the Desert", Palmyra boasted temples, colonnaded alleys and elaborately decorated tombs that were some of the best preserved classical monuments in the Middle East.

Situated 210 kilometres northeast of Damascus, its name means City of Palms. It is also known by the Arabic name Tadmor, or City of Dates.

Citadel of tombs and temples

Built on the Western model, "you could almost compare it to Rome", according to Marielle Pic, head of Oriental antiquities at the Louvre museum in Paris.

They city's temples were built after it was declared a free city by Roman emperor Hadrian in 129 AD, which allowed it to collect its own taxes.

Its richest residents built and sumptuously decorated a formidable necropolis of more than 500 tombs.

"One of the characteristics of Palmyra are the tall, multi-storey tower tombs in which the sarcophagi were laid," Pic says.

In the third century, Palmyrenes beat back the Romans in the west and Persian forces in the east in a revolt led by Zenobia, who became queen after her husband died in mysterious circumstances.

By 270 AD, Zenobia had conquered all of Syria and parts of Egypt. Her forces advanced into what is now Turkey before being defeated by the Roman emperor Aurelian near Antakya.

Site of notorious prison

Palmyra was the site of a notorious prison where hundreds of prisoners were massacred in the 1980s by the regime of Hafez al-Assad, father of President Bashir al-Assad. It was blown up by ISIS last year.

ISIS conquered the city on May 21, 2015. Three months later, the militants beheaded the city's's 82-year-old former antiquities chief Khaled al-Assaad and launched a campaign of destruction against its most treasured monuments.

First they destroyed the ancient shrine of Baal Shamin. In September, they demolished the 2,000-year-old Temple of Bel, a gem of Classical architecture. In October, they blew up the Arch of Triumph, dating from around 200 AD.

They also destroyed a dozen of the city's best preserved tower tombs.

Before ISIS captured the city, the Syrian government moved hundreds of artefacts from its museum to the capital for safekeeping.