In the summer of 1938, members of the American School of Prehistoric Research (ASPR) carried out an excavation in northeastern Bulgaria that would provide the first stratified sequence of Paleolithic occupations in the Balkans. The work took place at Bacho Kiro Cave, a limestone cavern near the monastery of Sveti Arkhangel, just outside the town of Drênovo.
The project came about almost by chance. Archaeologist Dorothy Garrod, then working with ASPR in Anatolia, was encouraged by colleagues O.G.S. Crawford and Christopher Hawkes to extend her research to Bulgaria, where many caves remained unexplored. Joined by James Gaul and Bruce Howe, Garrod traveled to Sofia in July 1938. With the support of the Bulgarian National Museum, led by Dr. Rafael Popov, and with permission from the Council of Ministers, the ASPR team established a small field season at Bacho Kiro Cave. Local speleologist Dimiter Bachev, who had first identified Paleolithic materials in the cave, guided them into the deeper galleries, while Mlle. Ivanka Akrabova of the National Museum joined the dig as interpreter and collaborator.
The excavation focused on the cave’s entrance and interior passages. In two main trenches at the entrance, the team identified a clear sequence of cultural layers extending from the Middle Paleolithic (about 50,000–40,000 years ago) to the Upper Paleolithic (roughly 40,000–20,000 years ago). The deepest levels (Layers K and L) contained Mousterian tools—scrapers and points made largely from quartzite and volcanic pebbles—associated with Neanderthal groups. Above them, Aurignacian layers (Layers E, F, and J) yielded end-scrapers, burins, retouched blades, and bone tools typical of early modern human occupations across Europe. Hearths and abundant faunal remains, especially cave bear bones, were also documented. Higher levels contained Neolithic pottery and more recent remains, marking later episodes of use.
This stratigraphy was crucial because it demonstrated for the first time in Bulgaria a sequence that paralleled broader European developments: a Mousterian phase belonging to Neanderthals, followed by Aurignacian industries made by early Homo sapiens. The Aurignacian finds connected Bulgaria with Central European and Near Eastern Paleolithic traditions, suggesting that Bacho Kiro lay along important prehistoric corridors linking the Balkans to wider Eurasia.
The team also explored deeper galleries within the cave, guided by Bachev. Here, they found additional flint implements and cave bear remains, though some appeared redeposited by water. The unusual presence of finely made tools deep inside the cave remains an unresolved question.
The Bacho Kiro project was brief—just two weeks in July and August of 1938—but it marked a turning point for Paleolithic research in Southeastern Europe. It established the cave as one of the key sites for studying human prehistory in the Balkans, a reputation it still holds today. Later research at Bacho Kiro has since revealed some of the earliest evidence of modern humans in Europe, but this initial ASPR-led season laid the groundwork by setting the sequence of occupations and demonstrating the site’s scientific importance.
Through international collaboration—between Harvard-affiliated researchers, Bulgarian scholars, and local supporters—Bacho Kiro became a cornerstone for understanding how humans and Neanderthals lived, interacted, and left their mark in the deep prehistory of Southeastern Europe.