Israeli archaeologists have discovered a huge hospital from the Crusader era in Jerusalem’s Old City, the Israel Antiquities Authority said in a statement Monday.

The massive building, in the area of the Christian Quarter known as the Muristan (based on the Persian word for “hospital”), was excavated by the IAA in cooperation with the Grand Bazaar Company of East Jerusalem. The dig was initiated after Grand Bazaar decided to open a restaurant at the site.

Archaeologists have only uncovered a portion of the complex, which covers an estimated 15 dunams (3.7 acres).

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The hospital was built by the Knights Hospitaller, a Christian military order. Also known as the Knights of Saint John, after John the Baptist, the order was founded around 1023 to care for poor and sick Christian pilgrims to Jerusalem. After the Crusaders conquered Jerusalem in 1099, the Hospitallers gained their own Papal charter, giving them the task of defending the Holy Land in addition to providing for pilgrims.

With ribbed vaults and massive pillars, the building was apparently exquisite. The ceilings stand over six meters (18 feet) high.

“We’ve learned about the hospital from contemporary historical documents, most of which are written in Latin,” said the IAA’s Amit Re’em and Renee Forestany, codirectors of the dig, in a statement. “These mention a sophisticated hospital that is as large and as organized as a modern hospital.”

The earliest description of the hospital comes from John of Wurzburg, a German pilgrim who visited Jerusalem around the year 1160. “Over against the Church of the Holy Sepulchre, on the opposite side of the way toward the south, is a beautiful church built in honor of John the Baptist, annexed to which is a hospital, wherein in various rooms is collected together an enormous multitude of sick people,” he wrote. “When I was there I learned that the whole number of these sick people amounted to two thousand, of whom sometimes in the course of one day and night more than fifty are carried out dead, while many other fresh ones keep continually arriving.”

He also noted the military role the Hospitallers played. “This same house also maintains in its various castles many persons trained to all kinds of military exercises for the defense of the land of the Christians against the invasion of the Saracens.”

The hospital was divided into wings according to patients’ ailments and conditions. In an emergency, the building could house up to 2,000 patients.

Contemporary accounts give a sense of the massive dimensions of the hospital. One tells of a staff member who failed to carry out the functions of his job properly. He was forced to walked the length of the building, which took several minutes, while other knights walked behind the man, whipping him. All the patients witnessed this spectacle.

According to other accounts, the knights cared for both men and women from all religions. There are even records of the hospital serving kosher food to Jewish patients.

Despite the grandeur of the building, the knights used the primitive methods that were typical of their time. There is an account of a patient’s foot being amputated for a minor infection, a procedure that ended up killing the woman. The knights were able to gain medical knowledge from the local Arab population, which placed a premium on medical expertise.

The building also served as an orphanage. Cowled mothers would leave unwanted children at the door, often a baby from a mother who had given birth to twins but couldn’t care for both children. When the male babies reached adulthood, they would join the Hospitallers.

After legendary Kurdish warrior Salah al-Din captured Jerusalem from the Crusaders in 1187, he built a palace near the hospital. He renovated the building, and allowed 10 Christian monks to stay in the hospital to serve the local population.

The structure collapsed in an earthquake in 1457. Some portions of the hospital survived, remaining in use through the Ottoman period. There were rooms that served as a stable, and archaeologists found the remains of horses and camels during the excavation.

Until the year 2000, the building, owned by the Muslim Waqf, housed a crowded fruit and vegetable market. Since then, it has stood empty just off the Arab market on David Street.

According to Monser Shwieki, project manager for the Grand Bazaar company, the new restaurant will be incorporated into the existing structure, and “patrons will be able to marvel at the magical medieval atmosphere at the site.”

He said that the site is due to open to the public this year.