Level 13
From Tardis Wiki, the free Doctor Who reference
Level 13 was the lowest level on the floor-plans of the Dalek City, being the access point to the city's secret incubation level.
In the decades after the Thal-Dalek battle, the Thal scientist Tryana explored Level 13 and found the passage to the incubation level. Fifty cycles after the battle, the First Doctor and his companions returned to the city and managed to locate Level 13's door. After they met the Dalek Supreme below, they brought two of its attendants up to Level 13 to be taken to the Thal City by Kreos' troops. (AUDIO: Return to Skaro)
