During the Roman era Europe was divided into two worlds, Roman and Barbarian, with a natural border being formed by the river Danube. The northern side was occupied by the German Quadi tribes who, assisted by Rome, established the first kingdom of Vannius (Regnum Vannianum) in Slovakia in around the year 20 CE.
In order to protect the northern frontier of the Roman Empire, the Romans began to build military settlements along the river Danube. Gradually they created a network of fortifications also known as Limes Romanus, the remains of which still exist in present-day Hungary and Austria. The most significant archaeological sites, classified as Roman monuments, exist in the Bratislava area, at Rusovce, Iža, Stupava and Bratislava-Dúbravka. During the Marcomannic wars, Roman legions penetrated deep into Quadi territory, while leaving a trace in a unique Roman inscription on the castle rock in the town of Trenčín (179-180 CE). During Roman Times, the significance of the Amber Road (an ancient trade route between Europe and Asia for the transfer of amber) increased considerably, as it was used for active trade between the Mediterranean and the Baltic. An important part of this route ran through the south-western part of Slovakia, where it crossed with the Danubian Road which connected Western Europe with the Black Sea. The importance of the Slovak territory as a cultural bridge during this period is also illustrated by the richness of archaeological finds. These indicate that the advanced Roman culture was maintained directly in Slovak territory.
The fall of the Roman Empire was followed by a temporary period of human migration which is relatively poor in monuments. During the 5th and 6th centuries, the Slavic ancestors of the present-day Slovaks arrived at and settled in the Carpathian Basin building hill forts in elevated places. As wood was their main building material, most of these hill forts have not been preserved. The movement of various ethnic groups is also evident from various archaeological finds. The Slavs fell under the military rule of the neighbouring nomadic tribe of Avars. After being defeated by Charles the Great, the Avars integrated with the domestic population and forever vanished from history.
The Celtic occupancy of Slovakia broke up at the turn of the millennia. However, many conquests of the Celtic civilisation, especially in handicraft production and iron metallurgy, have lasted until modern times.