The most prominent contrasts between the present-day dialects are found between northern and southern varieties. Northern varieties cover most of continental Greece down to the Gulf of Corinth, while the southern varieties are spoken in the Peloponnese peninsula and the larger part of the Aegean and Ionian islands, including the large southern islands of Crete and Cyprus. The most salient defining marker of the northern varieties is their treatment of unstressed vowels (so-called "northern vocalism"), while many southern varieties are characterised, among other things, by their palatalisation of velar consonants. Between these areas, in a contiguous area around the capital Athens (i.e. the regions of Attica and neighbouring parts of Boeotia, Euboia, the Peloponnese and nearby islands), there is a "dialectal void" where no distinctly marked traditional Greek dialects are found. This is due to the fact that these areas were once predominantly inhabited by speakers of Arvanitika Albanian. The Greek spoken in this area today is the product of convergence between varieties of migrants who moved to the capital and its surroundings from various other parts of the country, and it is close to the standard. On the whole, Standard Modern Greek is based predominantly on the southern dialects, especially those of the Peloponnese.