From around 500 BCE, the territory of modern-day Slovakia was settled by Celts, who built powerful ''oppida'' on the sites of modern-day Bratislava and Devín. Biatecs, silver coins with inscriptions in the Latin alphabet, represent the first known use of writing in Slovakia. At the northern regions, remnants of the local population of Lusatian origin, together with Celtic and later Dacian influence, gave rise to the unique Púchov culture, with advanced crafts and iron-working, many hill-forts and fortified settlements of central type with the coinage of the "Velkobysterecky" type (no inscriptions, with a horse on one side and a head on the other). This culture is often connected with the Celtic tribe mentioned in Roman sources as Cotini.