Midnight (Midnight), to make way for the time.
Talk about it here.
The planet's diamond-based geology was active. Diamond falls were a common occurrence. Midnight even had a Sapphire Waterfall. Earthquakes were thought to be impossible though. The planet had been left in silence for millions of years before humanity took over. The planet had no atmosphere and due to the destructive X-tonic radiation of its sun it was thought that no life was possible on the planet, be it carbon-based, hydrogen-based, silicates, gas beings or other. (WC: Monster File: Midnight)
Leisure planet Edit
Despite the hostile environment, the Leisure Palace Company turned it into a leisure planet to take advantage of its spectacular views. Since no human could walk on the surface or even touch the planet's diamonds, Leisure palaces were lowered from space. There was a spa, which had an anti-gravity restaurant, and a bus company called Crusader Tours offered sightseeing trips to the planet's picturesque locations, such as the Sapphire Waterfall, which had its own Waterfall Palace. Its other tourist attractions included Winter Witch Canyon and the Multifaceted Coast. Many of these tourist attractions were surrounded by large glass domes, providing protection from the X-tonic sunlight. According to Donna Noble, the travel brochures state that the glass in these domes is fifteen feet thick. (TV: Midnight)
On his visit to Midnight with Donna Noble, the Tenth Doctor found that some kind of life-form was able to survive on the planet's surface. This was proven when a mysterious being attacked one of the shuttle buses. After having barely survived the attack on the bus, the Doctor warned the company about the danger and the Leisure Palace was removed so whatever destructive force existed upon the planet was left undisturbed. (TV: Midnight)
Donna told her grandfather Wilfred about Midnight, and that it was made from diamonds. He relayed the story briefly to Rose Tyler when she saved him and Sylvia from a Dalek when the Earth was dragged to the Medusa Cascade. (TV: The Stolen Earth)