The region has been inhabited since prehistoric times and is a key area for the understanding of both Atlantic European, Megalithic and Castro cultures. Historically, Northern Portugal with Galicia in Spain, made up the Kingdom of Galicia. In protohistoric times, it was inhabited by Gallaeci tribes, related with the Lusitanians, and it corresponds roughly to Conventus Bracarensis of Roman Gallaecia. The historical Suebic Kingdom (5th-6th centuries AD) had its capital in the now Portuguese city of Braga and most of these migrants and invaders established themselves in Littoral Northern and Central Portugal, when the Roman empire collapsed. After the Islamic conquest of the Iberian Peninsula, a small county was established around the city of Porto, which expanded southwards and became a government, the County of Portugal in the 10th century. This county grew in ambition and it was where Portugal's first king, Dom Afonso Henriques, established the Portuguese kingdom and stated the southward expansion. The Portuguese language evolved from this area, and has a specific modern dialect, Northern Portuguese, taken down south as the Portuguese Kingdom expanded, namely after Afonso Henriques era.