Srangor was the planet where the Daleks and Kotris created their Temporal Chamber.
Geography
The surface of Srangor had many mounds, which the Doctor claimed were factories being used to build Dalek weapons. Large cities were present on the planet before the Daleks invaded. The Daleks had also burrowed to the core of the planet. Native animals to the planet were Petulins. (AUDIO: X and the Daleks)
History
At some point before 1893, the Daleks invaded Srangor, and enslaved the native population. Their cities were destroyed during this process.
By 1893, the Daleks had constructed a Temporal Chamber inside the planet, and the Dalek time controller used the planet as his base of operations. The Eighth Doctor and Molly O'Sullivan arrived in 1983 and met the locals of the planet, who lived in fear of the Daleks.
The influence of the Daleks on Srangor was erased after the timelines were re-written when Straxus killed himself. Because of this, the Daleks never invaded Srangor. (AUDIO: X and the Daleks)