"A naval base, with the Royal Navy's emblems, curiously amended. Efficient, bright-eyed women and men work briskly, everywhere you look. They are singing: hymns with unfamiliar words. Hard-faced Royal Marines watch you carefully, barring entry to the Geode's heart."
The Grand Geode is a secretive and mysterious base of the Admiralty (it is also called Station V). Well, technically it's an Admiralty base: the outpost is mostly independent, and behaves as a sort of auxiliary base for London's forces. The brass in London, even the Admiral, show significant concern about or even fear of whatever goes on there, often deflecting conversations about the port. This is due to the proliferation of the New Sequence, a splinter group dedicated to bringing the Dawn Machine's influence to the Neath. It has made this Geode their headquarters.
The Grand Geode is a place where powers not known to the average Londoner play to gain control of the Neath. Zee-captains should be wary, as attempts to explore and trade with these parties often result in their crew members being whisked away for unknown purposes, and the curious inability to recall what occurred during their stay.