Sesshōmaru's mother's manor

Sesshōmaru's Mother's Palace is a location that was first introduced in Chapter 467 of the manga, and Episode 176 of the anime.

History
Over five centuries ago in the, the rivaling beast kings of the West and East,Toga and Kirinmaru, had confronted the Grim Comet with Blasting Barrage and Meidō Zangetsuha from their respective swords as Kirinmaru's elder sister, Zero, and Toga's dog-demon wife had watched from the sidelines.

Inuyasha
Inuyasha had noticed a cloud shaped like a female dog, which carried Sesshōmaru's scent as he, Jaken, young Rin and eleven-year-old Kohaku arrived at the palace when Sesshōmaru requested his dog-demon mother to aid in mastering and fully developing the Meidō Zangetsuha technique. The lady of the Dog-Demon Clan had sat on a red chusion-like throne and showed her son her Meido Stone necklace that her estranged late husband had left her.

Hanyō no Yashahime
During a flashback narrative told by Riku in "Farewell Under the Lunar Eclipse", Sesshōmaru, Inuyasha, Kagome and Jaken arrive at the palace when the owner was away to take care of the incoming thret of the Grim Comet in place of the late Toga and the still-slubering Kirinmaru.

The palace made an appearance in "The Three Princesses Strike Back", where Kirinmaru visits the woman as he asks her about the Windmill of Time, following the recent incidents involving Zero and the Half-Demon Princesses.

Many months later, in "Zero's Wish," it is not seen but the pale yellow clouds surrounding it are seen as Kirinmaru confronted the Windmill of Time again, demanding why it would reject him, the strongest of demons, and he heard Akuru's pinwheel spinning and fled after the spirit of spacetime.