Her one decisive act is a substitution, and it worked because her husband did not look closely at what he was eating.
Cronus, warned that one of his children would overthrow him, swallowed each as Rhea bore it: Hestia, Demeter, Hera, Hades, Poseidon. Pregnant with the sixth, she appealed to her parents Ouranos and Gaia, and was sent to Lyctos in Crete. She bore Zeus there in the night, gave the child to Gaia to hide in a cave on a wooded mountain, and wrapped a stone in swaddling clothes. Cronus took it and swallowed it, and — Hesiod says — did not notice in his heart that his son had been left behind, unharmed.
The stone is the interesting part. When Zeus later forced his father to disgorge the children, the stone came up first, and Zeus set it at Delphi beneath Parnassus as a marvel for mortals. Pausanias saw it, in the second century CE, and reports that it was of no great size and that the Delphians poured oil on it every day and laid unspun wool on it at festivals. That is a physical object, in a known location, still receiving ritual attention eight hundred years after the poem that explains it.
Where in Crete, and who kept the baby quiet
The birthplace is genuinely disputed and always has been. Hesiod names Mount Aigaion near Lyctos. A strong tradition puts it on Mount Ida, where the Idaean Cave produced bronze votive shields and other offerings from the ninth century BCE. Another names the Diktaean cave at Psychro, also with substantial excavated votive deposits. Different Cretan communities claimed the honour and could show visitors a cave.
The nurses vary too: the nymphs Adrasteia and Ida, the goat Amaltheia whose horn became the cornucopia, and bees. The constant element is the Kouretes — armed young men who danced around the infant clashing their spears on their shields so that Cronus would not hear him crying. That detail preserves a real Cretan institution: an ecstatic armed dance performed by young men, attested in the hymn to the Kouretes found inscribed at Palaikastro, which addresses a "greatest Kouros" and asks him to leap for the herds and the crops.
The story explains a rite that existed, which is the usual direction of travel.
Rhea and Cybele: an identification, not an identity
Greeks meeting the Phrygian Cybele — the Mother of the Gods, worshipped in the mountains of Anatolia with lions, tambourines, ecstatic processions and the self-castrated priests called Galli — identified her with Rhea, on the reasonable ground that both were mountain-dwelling mothers of gods attended by noisy male dancers. The Kouretes and the Phrygian Corybantes were assimilated in the same move.
It is worth holding the two apart. Cybele has an independent Anatolian history going back at least to the Phrygian kingdom, her own iconography, her own priesthood, and a myth of Attis that has nothing to do with Rhea. Her cult was formally imported to Rome in 204 BCE, on a Sibylline instruction during the war with Hannibal, when the black stone from Pessinus was brought to the city — and Roman authors were markedly uneasy about the priests they got with it.
Rhea's Roman equivalent is instead Ops, an old Italic goddess of abundance and the consort of Saturn, with festivals in August and December. Three goddesses in a row, each identified with the last, each originally something different.
Her name, and the flowing
The ancient etymology, popular with the allegorists, connected Rhea to rheō, "to flow", making her the principle of flux — which Plato plays with in the Cratylus, pairing her with Ocean as the parents of a world in constant motion, and which the Stoics took seriously. Modern linguists do not accept it; the name has no secure derivation and may be pre-Greek, which is what one would expect for a mother goddess with strong Cretan and Anatolian associations.
She is called Rhea Kybele, Meter, or simply the Mother of the Gods in later texts, and Greek cities acquired a Metroon, a temple of the Mother, which at Athens doubled as the state archive — an odd and rather lovely arrangement in which the public records were kept under the protection of the mother of the gods.
What she does afterwards
Very little, and that is characteristic of the Titan generation once Zeus is established. She appears occasionally as an intermediary: she raises Persephone in some accounts, and at the end of the Homeric Hymn to Demeter it is Rhea who is sent down as the messenger to persuade Demeter to end the famine and rejoin the gods, which she does successfully. That is a well-chosen errand — a mother who once lost her children to her husband, sent to a mother who has just got hers back.
In Apollonius' Argonautica the crew sacrifice to her as the Mother of the Gods on Mount Dindymon and the earth responds with springs of water and the beasts fawning, in one of the poem's most striking scenes.
Almost no narrative, and therefore almost no afterlife
She is one of the least-used Greek deities in fiction, and for the same reason as Hestia: almost no narrative. Where she appears it is usually as the mother in a Titanomachy retelling — the Percy Jackson books, various games — or in a scene about the stone.
Her name survives most visibly in the sky. Rhea is the second-largest moon of Saturn, discovered by Cassini in 1672, and the Saturnian system is named consistently after Titans, which puts the whole family in orbit around the father who swallowed them. There is also the extinct genus and the modern flightless bird Rhea, named in 1752 for reasons its namer did not explain, and the plant fibre ramie, sometimes called rhea, which is unrelated.
The stone, the Metroon, and a goddess who kept being merged
Did Cronus really not notice the stone?
Hesiod is explicit that he did not, and the story depends on it. Some later authors, uncomfortable with a god being fooled by a wrapped rock, add that Rhea used a drug or that Metis was involved. The unembarrassed version is the older one, and it belongs to a wider folk-tale pattern of the swallowed substitute that appears across many traditions.
Is she the same as Gaia?
No, and the distinction matters for the succession sequence: Gaia is her mother, of the primordial generation, and is an active schemer across all three regime changes. Rhea belongs to the Titan generation and intervenes once. Later writers, and modern popular accounts, blur them into a general Great Mother, which erases the genealogical structure that the Theogony is entirely built on.
What is the Metroon?
A temple of the Mother of the Gods. The Athenian one, in the Agora next to the Bouleuterion, held the official copies of laws, decrees and public documents from the late fifth century BCE onward, and the state archive was maintained there. Other cities had their own. Its architectural remains have been excavated and it is one of the better-understood civic buildings of the Agora.
Does she have any cult of her own in mainland Greece?
Some, and mostly under the title Mother of the Gods rather than under the name Rhea. There are sanctuaries at Athens, Olympia, Sparta and elsewhere; Pausanias mentions temples and images. The distinctive thing is how much of that cult is really the imported Anatolian Mother wearing a Greek genealogy, which is precisely the problem that makes her hard to write about accurately.