Remains of buildings were found in the upper town of Halos between the walls running uphill. One of these buildings was a sanctuary dedicated to Demeter and Persephone. The building is 10.40 m long and 8 m wide. A partition wall divides the building into a northern and a southern half of equal size.
The walls of the sanctuary consist of two rows of stones with a fill of earth and small pebbles. Poros blocks were used to build the entrances to the building. The roof of the building was covered with roof tiles. Foundations, walls and tiles suggest a simple building.
The most intriguing feature in the southern half of the building was a rectangular pit that had been cut out of solid rock. Nine poros blocks had been placed along the sides of the pit and two poros blocks served as partition wall. Around and inside one of the pits flat slabs were found which originally had covered both pits.
Around the two pits and in the northern half of the building a large number of artefacts came to light: figurines, a relief, small hydrias (hydriskes), a life-size ceramic head and large fragments of stands for thuribles (thymiateria). Figurines and hydriskes point to a sanctuary dedicated to Demeter and Persephone.