Inside the square, a new, single-storey tower was built between the two towers. Lower Castlewho suffered the same fate. It was destroyed during the Second World War. Restoration and maintenance work on the medieval castle began in the 1970s. The vegetation was cleared and removed, the walls along the access road to the castle were rehabilitated, the outer wall between the SE and SW towers was rebuilt, and the SE tower was completely rebuilt and covered with shingles. All work was suspended in 2002 and has not been resumed to date. The square and the castle have been declared a national monument owned by the State by decree. Since then, archaeological investigations have been carried out alongside the construction works. This autumn, archaeological research was carried out inside the square by the ZVKDS CPA team. The municipality of Kostel wanted to improve and extend the footpath from the square to the castle. Four buildings were documented on a 45.5 m long and 2.3 m wide strip, but they were not fully investigated because the walls of the buildings extend beyond the excavation field. The first two were located just below the church, where there is now a grassy area. The largest survives as a wall 3.9 m long, 0.45 m wide and 1.10 m high. It was oriented in a west-east direction. A smaller wall, 0,60 m long, 0,30 m wide and 0,60 m high, was perpendicular to it. The walls were dug into the geological bedrock. The interpretation that they were buildings is supported by the fact that the space between the walls was filled with rubble containing a screed of compacted sand and mortar, fragments of wall plaster, numerous fragments of medieval pottery, iron nails and a newt to the value of one sold (Domenico Contarini, 1659-1674).
Just off the path that branches off from the present-day main route of the market town towards the castle, we documented the remains of the basements of two former buildings that were dug into the hillside. The two buildings were situated perpendicular to the present road. In addition to building materials and pottery fragments, the ruins also contained layers of charcoal, suggesting that the buildings were either damaged or destroyed by fire. An intact prehistoric walking surface with numerous pottery sherds and stone sherds was also discovered in the area between the two buildings.
Archaeological excavations have uncovered part of the ruined buildings within the western part of the settlement. The archaeological research confirms the appearance of the settlement on the Valavasor Veduta and raises new questions about the settlement, development and decay of the castle and the Kostel square.