The bridge "um Streymin" between Streymoy in the west and Eysturoy in the east has been connecting the two banks of the Sundalagið at the narrowest point of the sound since 1973 . The bridge also forms the border between the village of Oyrarbakki in the south and the village of Norðskáli in the north.
The largest commune in the region is the Sunda kommuna , which today includes areas on both islands. The Tórshavnar kommuna extends further south on the Streymoyer side, as does the Sjóvar kommuna on the Eysturoyer side. The municipality of Eiði in the north of Eysturoy finally lies entirely in the Sundalag.
Common to the residents on both sides of the sound is their dialect of the Faroese language , which is part of the Eysturoy / North Islands dialect.