Planet Altea or Altea is a planet in several incarnations of the Voltron Franchise.
Beast King Golion
A long time before the events of the series, the lions of Golion landed on Altea. They were discovered by the royal government, and the lions' lairs, and the transports system used to shuttle the pilots, was completed by the early 1980's.
The Galra Empire attacked and invaded Altea in 1984. The Galrans captured King Raimon, his wife, and his children. The king refused to surrender, so under Daibazaal's order, Zadak executed them. The Galrans took most of the Alteans as slaves.
But the then one-year old Princess Fala was rescued by Raible. They hid in the ruins of the royal castle for the next fifteen years, with Raible raising Fala. The Alteans who remained on the planet hid in caves and bunkers.
In 1999, five space explorers from Earth crash landed on Altea while trying to escape from Galra. They meet Raible and the princess and become partners with the lions, bringing back Golion.
Altea is attacked by Galra several times over the next few months. In 2000, the Leo Alliance is formed, with Fala as its leader. The alliance soon takes down Galra.
Voltron: Legendary Defender
In Voltron: Legendary Defender, Altea was the home planet of Princess Allura, her father King Alfor, Coran, and the Space Mice. The birthplace of Voltron, it was attacked by Zarkon's Galra Empire 10,000 years ago, with Alfor choosing to hide the Voltron Lions and Allura rather than have Voltron formed to battle their enemy. Sadly, Altea and all the planets in its solar system were utterly destroyed as a result, with only the six residents of the Castle of Lions being known to survive the tragedy. This left the Galra Empire virtually unopposed in its efforts to conquer the galaxy over the course of the subsequent ten millennia, until Allura was awakened by the future Paladins of Voltron.
Alteans as a species are known to have minor shape shifting abilities that allow them to adapt to new environments and blend in with the local populations. Alteans are also known to have lifespans vastly superior to those of humans, as Coran remembers the construction of the Castle of Lions, which happened six hundred years prior to his and Allura's stint in stasis for ten millennia. Coran is at least a bit or more older than six hundred years old, yet appears as a middle aged man by human standards. This may be due to the Altean aging process being slower than that of humans, or Coran may be using his own shape shifting abilities to appear somewhat younger. Regardless, the Alteans are certainly a long lived species.
Apparently, razor-sharp and boiling-hot rocks fall from the sky from time to time on Altaea.