Alba Iulia Fortress built
1715 CE.
Shown on the map at 46.067°, 23.574°.
The Alba Carolina Citadel (Romanian: Cetatea Alba Carolina, Hungarian: Gyulafehérvári vár) is a star fortess located in the center of Alba Iulia, Romania. Its construction commenced on 4 November 1715, during the Habsburg rule in Transylvania, and was completed in 1738. 20,000 serfs were involved in its construction, which is estimated to have cost around 3 million florins. The citadel was built on the site of two other fortifications: the legionary fortress of Legio XIII Gemina (known as Apulum), as well as the medieval Belgrad citadel.
Text from the Wikipedia article Alba Iulia Fortress, licensed CC BY-SA 4.0.