Casegas is one of the oldest villages of the ADERES parishes, with historical references that go back to the XII century. It belonged to the Order of the Templars, later the Order of Christ, looking after a vast territory, including areas that currently belong to the parishes of Erada, Sobral de S. Miguel (former Sobral of Casegas!) and S. Jorge da Beira. Along its drainage basin there are fertile alluvium deposits that allow a wide variety of crops, there are records of the existence of 20 mills and 5 wine presses, testimonies of some opulence that are still visible in the parish seat, in residencies with manorial characteristics, from schist and granite and examples of religious architecture, including the main church and the emblematic Chapel of Souls.

The toponym Ourondo probably derives from gold, certainly there, like in other riverside villages of the region, exploited by mining the sand of the Zêzere. Hence, currently the great richness of Ourondo is its biodiversity and landscape. The Zêzere meanders and twists tortuously and, perpendicularly to its bed, stone walls have been erected to protect mud flows from floods and erosion, the so-called terraces, forming a compartmentalised landscape of real mosaic riverside habitats (meadows, riparian galleries, gravel banks and sandbanks), with agricultural areas, and olive groves and pine forests at slightly higher levels.