The hypothesis of a Dacian occupation of Slovakia during the 1st century BC is contradicted by the archaeological evidence that this region featured a predominantly Celtic culture from c. 400 BC; and a sophisticated kingdom of the Boii Celtic tribe. Based in modern-day Bratislava during the 1st century BC, this polity issued its own gold and silver coinage (the so-called "Biatec-type" coins), which bear the names of several kings with recognised Celtic names. This kingdom is also evidenced by numerous Celtic-type fortified hill-top settlements ("oppida"), of which Zemplin is the foremost example in south-east Slovakia. Furthermore, the archaeological Puchov culture, present in Slovakia in this period, is considered Celtic by mainstream scholars. Some scholars argue that Zemplin was occupied by Burebista's warriors from about 60 BC onwards, but this is based on the presence of Dacian-style artefacts alongside the Celtic ones, which may simply have been cultural imports. But even if occupation by Dacian troops under Burebista actually occurred, it would probably have been brief, as in 44 BC Burebista died and his kingdom collapsed and split into 4 fragments. In any case, it does not follow that the indigenous population became Dacian-speakers during the period of Dacian control. Karol Pieta's discussion of the ethnicity of the Puchov people shows that opinion is divided between those who attribute the culture to a Celtic group – the Boii or Cotini are the leading candidates – and those who favour a Germanic group e.g. the Buri. Despite wide acknowledgement of Dacian influence, there is little support for the view that the people of this region were ethnic Dacians.