He designed a number of notable buildings in Istanbul during the late period of the Ottoman Empire and in Ankara and other cities of Turkey in the early years of the Turkish Republic as a member of the First national architectural movement.
During the reign of Sultan Abdulmejid I (r. 1839–1861), Luigi Mongeri was appointed to a hospital in Istanbul in 1857, and was promoted to the position of the chief physician in 1860.
During the reign of Sultan Abdulaziz (r. 1861–1876), he was appointed chief physician of the newly established psychiatric hospital in 1873.
He then continued his education studying architecture at Accademia di Brera in Milan, where his uncle Giuseppe taught.
[1] Giulio Mongeri married to Italian-descent Caterina Capodaini (1877–1900), nicknamed Ketty, he met during a summer holiday in his brother's house on Büyükada, Istanbul.
He lived with his children and the nannies in the beginning in Pera, today Beyoğlu, and later in Şişli in houses he designed and built.
[1] In 1909, Mongeri was appointed to teach in the Architecture Department at the School of Fine Arts (Ottoman Turkish: Sanayi-i Nefise Mektebi), today Mimar Sinan Fine Arts University in Istanbul, which was one of the first institutions in the Ottoman Empire under the direction of Osman Hamdi Bey (1842–1910) to provide architectural education in western manner.
With the outbreak of the Italo-Turkish War (1911–1912), some Italian-origin people in the Ottoman Empire were forced to leave the country.
The Municipality of Milan sent Mongeri a certificate of appreciation for his aid and support to his exiled siblings during the war time.
[1] Some of notable Turkish architects he taught are Arif Hikmet Koyunoğlu (1888–1982), Macit Rüştü Kural (1899–1964), Şevki Balmumcu (1905–1982), Zeki Sayar (1905–2000), Sedad Hakkı Eldem (1908–1988) and Hüsnü Tümer.
[1] Mongeri designed a number of notable buildings primarily in Istanbul, but also in Ankara, Bursa and some other cities between the 1900s and 1930s.
[2] Mongeri's known first work was his design of the Church of St. Anthony (1906–1912),[3] and apartments,[4] together with Italian-Levantine architect Eduardo de Nari.
The ceilings of the headquarters of Ziraat Bank and İşbank were decorated with stained glass of European floral motfs.