The hearth in the throne room of the gods is a magical flame that glows brighter when the gods are at their strongest. However, it is shown to get colder and harder to keep alive when enemies approach (such as the Titans) or when the gods are weakened. Since it is tended to by Hestia, goddess of Home and Hearth, it is considered to be a place of rest and a sign that all gods are welcome at Olympus. Nevertheless, if Olympus is ever attacked or worse, conquered by enemy forces, the flame of the hearth will die. In this event, Olympus would no longer be considered the home of the gods and may be lost forever, preventing the gods from moving on. Even if the flame of the hearth goes out, Hestia, being the 'last Olympian',  would still exist in other hearths, as she is not tied to the hearth on Olympus in the same way that the other Olympians are tied to their thrones.
Percy sees the hearth in the Hall of the Gods once again when he revisits Olympus.
Percy sees Hestia stoking the hearth. As the group of demigods approach her, she mentions that Percy now has the Curse of Achilles, but is blind to the truth. She then shows him a vision of the time that Luke Castellan and Thalia Grace first met Annabeth Chase. The vision only lasts a second in real time and the group eventually leaves the hearth.
The hearth is visited once again after Percy has a talk with Prometheus about the demigods defending Olympus surrendering. As Percy holds Pandora's Pithos, he gives it to Hestia to watch over it, as hope is strongest at the hearth.
Later, when Percy battles with Kronos in the Hall of the Gods, Kronos' scythe is knocked into the hearth. When he reaches for it however, Hestia appears and causes the flames of the hearth to erupt, eventually melting the scythe with the heat of the flames.
- The campfire at Camp Half-Blood is modeled after the hearth on Olympus, as it stands in the center of the god's cabins (like the thrones on Olympus) and it changes color to reflect the mood of those around it.
- When Percy Jackson first arrived at Camp Half-Blood in The Lightning Thief, he saw Hestia tending to the fire. This scene is reflected in The Last Olympian, as Percy walks into Olympus and finds Hestia there tending the hearth.