Aglientu is located a few kilometres from the sea, in an area predominantly rich in granite. Its landscape is characterised by majestic boulders and green valleys that slope down towards sandy shores with high desert-like dunes alternating with imposing cliffs. Just like Monti Russu, a pink granite relief with a rounded shape extends towards the Gulf of Asinara. The 22-kilometre-long coastline, with extensive unspoilt stretches, is renowned for the beautiful beaches. Amongst the largest is Rena Majore (on the border of the Santa Teresa Gallura territory), Litarroni and Vignola, a fishing village where a Spanish tower from 1606 stands 12 metres high, from which a panoramic view of the sea and inland can be enjoyed.

The name of the town has Latin roots, with the meaning of white, also being present in other place names in the area (Montagliu, Agliacana, Frati Agli and Agliu).