The TARDIS (Time and Relative Dimension in Space) is The Doctor's time travelling space ship, which, in addition to its time travelling capabilities (it can go anywhere in Time and Space), has significantly larger dimensions in the interior than the exterior ("it's bigger on the inside!"). TARDISes have the ability to change the appearance of their exterior to blend in with their surroundings. The Doctor's TARDIS, however, is stuck in the shape of a 1960s police telephone box after The Doctor landed in London in 1963.
This cache also marks the start point for my Doctor Who Travel Bug Race entry, which is aiming to reach a cache in Canada (GCP8TM)
The cache itself is hidden on a public footpath between Woodseaves and High Offley, and can be taken in as a vaguely circular walk with other caches in the area.