Tellus IV

 was a planet of the Gardeners.

Originally it was a hot, barren world. The Gardeners brought there topsoil from their home world. Eventually, they turned the planet into a garden that smelled of freshly mown grass and had sheep dotting the landscape.

The Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yaz visited it by the invitation of the Gardeners. (PROSE: The Secret in Vault 13)