Olympus, like Asgard, was one of the first realms to fully manifest after the Demiurge surged into awareness. The entrance to Olympus was placed atop the peak of Mount Olympus in the nation now known as Greece.
The current Gods of Olympus include Zeus, the primarch; and his siblings, children, and cousins. The prime pantheon is Hades, Poseidon, Hera, Hestia, Demeter. Notable children include Ares, Apollo, and Artemis. Several potent ideologues representing abstractions such as Anger or material concepts like the Ocean also exist. The shades of the first generation of Olympians, the Titans, can be found scattered among the vast realm as well. Except for a handful of Titans, most of the gods of Olympus are progeny of Zeus or his immediate siblings.
Olympus' proximity to the human world has allowed them to have a substantial influence on the formation of culture. Beginning with the rise of Atlantis, the Greek pantheon provided insight and wisdom for many mortals and directed the earliest of societies. After Ragnarok broke the Demiurge, Olympus was one of the few realms that could maintain any semblance of contact with humanity. They were among the first to restore contact with human worshippers before the Demiurge was fully restored.
Olympians are truly immortal and almost impossible to kill. Every Olympian is directly related to Gaea, and through her, closely connected to the Demiurge. They wield immense magical powers, particularly when in defense of their personal idealogical domains-- even when off Olympus.
The chief gift of Olympus to the realm of Man was the creation of the Amazons of Themyscira. In the event Ragnarok struck again, the Amazons were intended to preserve human knowledge and aid in restoring humanity. Their champion, Diana, is born of Olympus and Man, and is among the greatest warriors alive in any realm.
At first, Olympus was populated by primordial forces given sentience. Gaea attracted many ideologues with her gentle nature, and they manifested with notions such as Love, emotions like Anger, and concepts such as Mountain and Ocean.
It was her progeny Uranus who was the first of the New Gods of Olympus to walk through that land. He and Gaea shaped Olympus into a realm of remarkable beauty, the forces of nature arraying themselves around his will as he shaped it to his vision.
From Uranus and Gaea would come the first generation of his progeny. Due to their close relationship with Gaea, the Titans are arguably closer to the Elder Gods in power and capability. They numbered twelve in all. Seeking more godlings to add to his power, Uranus demanded Gaea bear him more children. She brought six more beings into life: the Cyclopes and the Hecatoncheries. Uranus hated these youngest and bound them to the darkest bowels of Tartarus, finding them ugly and their lack of magic a disappointment. Their misery and resentment grew so great that Tartarus began to border other infernal realms, such as Hell.
Angry, Gaea demanded of the Titans that one among them castrated Uranus and take the power of Olympus from him. The youngest Titan, Cronus, attacked his sleeping father and castrated Uranus. From the blood spilled rose up the Furies, the Gigantes, and the nymphs. Uranus' testicles were absorbed by the spirit of the ocean, and from them grew the goddess Aphrodite.
Cronus betrayed his mother's wishes, and imprisoned his brothers-- the Giants, the Hecatonchires and the Cyclopes-- in Tartarus once more. He set the dragon Campe to guard them and with his sister, Rhea, Cronus assumed his role as Primarch of Olympus over the other ten Titans. Their proximity to Earth allowed the Titans to take on a role of mentorship over the tribes in the Mediterranean, which contributed greatly to the swift rise of Atlantis.
Prophecies gleaned from his weakened father led Cronus to suspect his children would betray him. He swallowed his children whole as they were born. Finally, Rhea and Gaea conspired to hide his youngest son from him. Cronus was tricked into eating a rock, and Zeus was delivered on the shores of Crete.
When the World Tree was shattered, Olympus' harmony was lost. It was at this time that Gaea urged her children to rise up again and retake Olympus while Cronus no longer had the unlimited power of his godhead. Zeus returned to Olympus and united with his cousin Metis, a daughter of the Titan called Oceanus. She gave him the same sickle used to castrate Uranus, and Zeus slashed Cronus' belly open. His five siblings spilled forth, fully grown and none the worse for wear. But Cronus rallied the Titans and drove Zeus and his siblings off before the final blow could be delivered.
Facing the prospect of war with his extended family, Zeus dove deep into the bowels of Tartarus. He freed his uncles the Giants and enlisted them as an army. He also freed the Cyclopes and the Hecatonchires. The Cyclopes forged weapons of great power for Zeus and his brothers-- thunderbolts for Zeus, a trident to command the seas for Poseidon, and a helmet of darkness for Hades.
Thus began the vast war called the Titanomachy, in which the upstart Zeus and his siblings overthrew the rule of Cronus and the Titans. Zeus imprisoned the defeated Titans in the pits of Tartarus where the Hundred-Handed and Cyclopes had been imprisoned. Oceanus was bound under the ocean in elemental chains he could not break. Zeus promised life to the desperate Atlanteans of the nearby ocean and they became The Blue, tasked with guarding Oceanus' prison for all time.
Several of the Titans who aided Zeus or demurred from joining the battle maintained their freedom, but were substantially depowered as Zeus became the arch-deity and the harmony of Olympus changed once more.
Zeus' new position made him indifferent to the uncles who had helped him conquer Olympus and he forced them underground, to occupy realms out of sight and to ensure the Titans did not escape their prison. The remaining Titans were conscripted to serve specific roles in serving the New Gods of Olympus.
Enraged that her children were once more imprisoned, Gaea allowed her brother Chthon-- the malignant First God-- to sire with her a mighty creature of vengeance called Typhon, while Olympus was still cut off from Earth. Typhon attacked Olympus and nearly destroyed it entirely, literally a personification of Gaea's wish to cleanse the history of violence. Zeus managed to defeat the creature and bound it permanently under Mount Etna in Greece, thus securing his rule forever.