Borkovský carried out excavations on an early Slavic burial ground in Loreto Square in front of Prague's Czernin Palace in 1934–35.[1][2] He also led the excavation of a medieval burial ground in Bartolomejska Street in 1936, ahead of the construction of a new police headquarters.[2] Between 1932 and 1936 he also managed the cataloging of the archaeology collection of the Josef Antonín Jíra Museum.[2][1] It was here that he discovered the first early Slav ceramic artifacts that proved the presence of those people in Bohemia in the early 6th-century AD.[1] Borkovský published his findings in the book Old Slavonic Ceramics in Central Europe which he produced at his own expense in 1940.[2] Borkovský transferred to the Czech State Archaeological Institute in the same year.[1]