Varna Chalcolithic Necropolis 

The Varna Chalcolithic Necropolis is a burial site in the western industrial zone of Varna, internationally considered one of the key archaeological sites in world prehistory. The oldest gold treasure and jewelry in the world, dating from 4,600 BC to 4,200 BC, was discovered at the site.
The site was accidentally discovered in October 1972.
A total of 294 graves have been found in the necropolis, many containing sophisticated examples of metallurgy (gold and copper), pottery (about 600 pieces, including gold-painted ones), high-quality flint and obsidian blades, beads, and shells.
The artifacts can be seen at the Varna Archaeological Museum and at the National Historical Museum in Sofia.