Some science behind the scenes

Mundus Cereris

During Roman and Etruscan times,  any site found to produce spiritual experiences was marked by a stone.  Usually a pit or ditch was dug,  to concentrate the 'energy' at that spot.  Known as the mundus Cereris, many cities of Latium and Etruria were actually founded around such places.  Plutarch in his ‘ Life of Romulus’  ch. 11 describes the custom of a mundus as being of Etruscan origin.  The Latin word mundus simply meant "world", but it signified the entrance to the ‘other world’ the spiritual world which clearly has no physical existence. Festus, quoting Cato, said:

 Mundo nomen impositum est ab eo mundo qui supra nos est.
(The mundus gets its name from that world which is above us.)

In Rome itself, the mundus was located in the Comitium, on the Palatine Hill. This stone was ceremonially opened three times a year, during which “spirits of the blessed dead (the Manes) were able to commune with the living”. Macrobius, [Macrobius, SaturnaliaI 16.18 ]quoting Varro, says of these days that:

 Mundus cum patet, deorum tristium atque inferum quasi ianua patet.
("When the mundus is open, it is as if a door stands open for the sorrowful gods of the underworld.")

It is virtually impossible to discern when visiting a sacred site, however, what kind of site you have found from this type of marker. 

Observations

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