Watch Free Online on Hurawatch. Monte Castelo is a fluvial shell midden, an artificial island, which was built and occupied from at least 6 thousand years. Located in the Guaporé river basin, in Rondônia, this site was excavated for the first time by archaeologist Eurico Miller in the 1980s. Thirty years later, it was located again by a team of archaeologists and the excavations were resumed, starting a new stage of surprising discoveries.