Tellus IV

 was a planet of the Gardeners.

It was not far from Calufrax Major.

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.

All types of gardens and greenhouses were represented on the planet, including walled gardens, wild gardens, zero-G gardens, hanging gardens and hanging baskets. The glasshouses of Tellus were considered architectural achievements.

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