Complex sentence: Near to that point was the most known Necromancy (Νεκρομαντειο) of the Ancient world which is still saved as a monument and it's been chronologized at the early Hellenistic era (4th-3rd century BC).
Split into simpler sentences: Near to that point was the most known Necromancy (Νεκρομαντειο) of the Ancient world which is still saved as a monument. It has been chronologized at the early Hellenistic era (4th-3rd century BC).