Villages of sunken huts with stone ovens appeared in Transylvania around 600. Their network was expanding along the rivers Mureş, Olt and Someş. The so-called "Mediaş group" of cremation or mixed cemeteries emerged in this period near salt mines. The Hungarian and the Romanian vocabulary of salt mining was taken from Slavic, suggesting that Slavs were employed in the mines for centuries. Bistriţa ("swift"), Crasna ("nice" or "red"), Sibiu ("dogwood"), and many other rivers and settlements with names of Slavic origin also evidence the presence of Slavs in Transylvania.