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In page Celts:
"The Celts also expanded down the Danube river and its tributaries. One of the most influential tribes, the Scordisci, established their capital at Singidunum (present-day Belgrade, Serbia) in the 3rd century BC. The concentration of hill-forts and cemeteries shows a dense population in the Tisza valley of modern-day Vojvodina, Serbia, Hungary and into Ukraine. Expansion into Romania was however blocked by the Dacians.[citation needed]