Castle Tersurus

Castle Tersurus was a castle located on the planet Tersurus which was designed by an architect.

History
The construction of Castle Tersurus was influenced by and the Ninth Doctor, both of whom separately and repeatedly travelled back in time to bribe the architect, who they communicated with in his native Tersuran, to make the other fall into traps while anticipating that they would later bribe the architect to do the same.

While the Master bribed the architect to create the Spikes of Doom as a trap in the castle, the Doctor countered this by travelling further back and bribing him to make the Sofa of Reasonable Comfort instead. Anticipating this, the Master travelled even further back, creating in a piece of masonry which he would later use in an attempt to crush the Doctor, however, the Doctor travelled further, resulting in his survival as the masonry was made hollow.

These bribes were made all in anticipation of the Doctor and the Master's confrontation on Tersurus, arriving in their TARDISes a hundred years after the Master first travelled back to meet the architect from his perspective, with nobody setting foot on the planet in the interim. The Doctor had arranged this meeting with the Master to inform him of his intention to marry his companion Emma. Ultimately, it was the Doctor who prevailed against the Master, having travelled in his TARDIS further back than the Master ever did, he had dinner with the architect and suggested he place a lever-operated trapdoor leading to the vast sewers of Tersurus at a spot where the Master fell before he could go back and make his own suggestion regarding a trapdoor.

As a result, the Master was forced make his way out of the sewers of Tersurus, a journey which took him 312 years. After doing so, the Master found his TARDIS which he used to escape and join with the Daleks, who only accompanied him as they had no noses, before returning to the "present day" shortly after he originally fell, confronting the Doctor and Emma at Castle Tersurus. Having had his body modified with Dalek technology, the Master attempted to kill the Doctor only to fall down the trapdoor again, forcing him to spend another 312 years making his way out before returning to the present, at which point the Doctor and Emma attempted to flee. While making pursuit, the Master was inadvertently knocked over the trapdoor by a Dalek, making his return only after spending a grand total of 936 years within the sewers of Tersurus. Before they could escape the Castle Tersurus, the Doctor and Emma were captured by the Daleks, who brought them aboard their spaceship. (TV: The Curse of Fatal Death)

When the Eighth Doctor saw a vision of the Ninth Doctor and Emma in a Tomorrow Window, he described Castle Tersurus as "unconvincing medieval dungeon." (PROSE: The Tomorrow Windows)