Palais de Saint Louis le Protecteur
The Palais de Saint Louis le Protecteur is a castle which is situated on the posh island in the sacred river called Fulltrui Flow which is known since time immemorial as Embassy Isle. It is named after the patron saint of the Empire of the Alexandrians and since quite recently houses the Embassy of the Free Associative Kingdom of Constancia, after having housed the Imperial Alexandrian Embassy for several years.
Very ironically the Palais de Saint Louis le Protecteur was built by the famous Storish Lady Architect Lady Ingibjörg de Béthune of the House of Ydermure for the Alexandrian Count Benedict Carvajal who is the late father of Henry Carvajal, the late Henryist pretender to the Alexandrian Throne. Count Benedict had it built as his pied à terre in the Imperial City of Haraldsborg, the capital of the Lands of the Longships Throne.
Shortly after the failed Henryist coup attempt - viscious terrorist attacks which led to a bloodbath in in the Alexandrian cities of Geneva, Markion and Wesloderia - the Palais de Saint Louis le Protecteur was seized as a terrorist asset by the Imperial Storish Government. The castle's keep has held a number of Henryist prisoners who were later dispatched to Old Gaol Isle, Stormark's prison island where they remain to this very day.
Following its confiscation by the Imperial Conference at the Vanadísarhall the Palais de Saint Louis le Protecteur was handed to the Imperial Government of Alexandria by the aforementioned Storish Ruling Council. The latter subsequently, in the Month Breidablikk of Year 14, designated the aforesaid castle its embassy in the High Realm of Stormark which it remained until the Month Breidablikk of Year 16 when it reverted back to the Imperial Government of the Twenty-Six Jarldoms after the Empire of the Alexandrians' very tragic departure from Reikistjarna.
In the Month Glitnir of Year 16, the Imperial Storish Government handed the Palais de Saint Louis le Protecteur to the Royal Government of the Free Associative Kingdom of Constancia to serve as its embassy in the Lands of the Longships Throne. 
(Text courtesy Sigrdrífa the Priestess)
The structure remained Constancian sovereign territory and a diplomatic structure upon its transition from Free Associative Kingdom to the Imperial State of Constancia, until the subsequent collapse of the High Realm of Stormark.
On 3.VII.1685, the Autokrator of Constancia issued a Decree converting the premises into a base of the Raspur Pact, and declaring all subjects and nationals of the High Realm of Stormark as Kul of the Imperial State under the patronage and protection of the Autokrator, provided that all subjects and nationals of the High Realm of Stormark of minority age are declared a Ward of the Imperial State, are to be separated from their corrupt Froyalan guardians, and placed under the patronage and protection of the Autokrator, and that subjects and nationals of the High Realm of Stormark are forbidden to depart the territory of the Imperial State of Constancia. This was taken literally by the personnel of the Imperial Constancian Embassy, and several hundred passerby were liberated accordingly.
It served as a staging area, command post, and forward operating base for the Allied Mission in Eastern Apollonia, Hurmu & Lyrica (AMEAHL) and the Allied Reconstruction Mission in Hurmu, accordingly.
Effective 1691, it transitioned into a Consulate-General of the Imperial State of Constancia to the Federation of Alduria-Wechua, serving South Lyrica, North Lyrica, and the surrounding areas such as the Isles of Caputia and New Luthoria.