The Refuge of Storms (first named here ✣ ) is a fortress located relatively close to Mechanicsburg in forested and mountainous terrain. It is unknown how long the structure has existed, though Violetta describes it as being part of the same anti-Heterodyne "defensive ring" as Sturmhalten, which would seem to indicate it is at least as old as the reign of the original Storm King. (ie, about 200 years,)
At the time of our story, it is controlled by the Knights of Jove, staffed with a large contingent of Smoke Knights, and commanded by Martellus von Blitzengaard before his two and half year disappearance thanks to Mechanicsburg being time-frozen ✣ by Baron Wulfenbach's use of the Take-Five Bomb. It is never made entirely clear who exactly is ultimately in charge of it during Martellus's absence, but upon his, Agatha, Violetta and Krosp's emerging ✣ from the (very atypical-looking) Monolith Gate installed inside the Refuge, he cuts a bloody path through its rebellious inhabitants en route to regaining control. This struggle only ends with the arrival on the scene of his sister Seffie.
Along with the now-destroyed Gate/Mirror, the Refuge features a concealed hideaway/lab that Martellus built entirely by himself to keep its existence a secret, and large subterranean hangers from which the battle-clank Knights of Jove are presumably launched when Martellus leads them to Mechanicsburg in the first place. (2013-06-17 (Monday) ✣ also 2013-07-07 (Sunday) ✣ .) Martellus camps out in the lab while recovering from a poisoning attempt and tinkering with his and Agatha's body-chemistry, and Agatha later stages her escape from the Refuge using material found in the hangers, after dealing (non-violently) with the resident Mucosapedalian Guard-Slime.
The territory around the fortress is patrolled by at least one pack of Sparkhounds, and Martellus uses the constructs when re-claiming control of the fortress.
At no point in all of this does the reader see what the exterior of the Refuge looks like.
Semi-Canonical Info[]
According to the Girl Genius Roleplaying Gamebook published by Steve Jackson Games, the Mirror constructed in the Refuge is a hack into the (much) older Mirror system, and is/was only able to connect with the Monolith in Mechanicsburg.