Eluria - 17 B (Dominaria)
Eluria rests in the middle of Dominaria's ocean, at the bottom of the deepest trenches. The nearest island to this point is hundreds of miles away. The surface weather is never pleasant; often times stormy, always windy with high waves.
Being deep blue dwellers, the native inhabitants of Eluria are, of course, very reclusive, and did not construct their home with visitors much in mind. However, friendly visitors may reach the base via Leviathan-transport. This is a more-or-less domisticated Leviathan which has been trained for the sole purpose of "swallowing" ships and other above-sea dwellers, then bringing them back to Eluria. It is big enough that it can swallow a whole army at a time, which is to say, it is also bigger than Eluria itself, and virtually impervious to assault. Phyrexians beware: very mean fish, squid thing, don't even try to harm it. It will only transport friendly units. Thankfully though for unfriendly units, it's non-combative (too wild for controlled combat), and will not attack except to protect itself in defense. In exchange for transporting services, the Elurian's help feed the creature by luring large schools of fish, using magic and the abundance of blue mana available in this area. If the Leviathan were not fed methodically, it would no doubt start feeding on whatever else it could find on its own. Which would of course require killing it, but that would probably lead to the destruction of a whole army in the attempt; so it's best just to feed the damn thing. Or else, go live someplace else. But the Elurian's like it here
Eluria itself is a walled, citadel-structure shaped out of diamond-like crystal, it is very beautiful to those inclined to say so. Eluria in its entirety is made up of one solitary, continuous piece of crystal, shaped by generations of ancient magicians, by a planeswalker, or even perhaps by Urza himself. Nobody really knows anymore. Only that the structure is as pristine and finely-crafted as the greatest sculptures of art, and yet will sustain heavy forces before hinting even the slightest crack. The inside of the castle-structure is spacious, and can accomodate an army of creatures of up to gargantuan size, colossal creatures and over have to reside outside next to the leviathan. The levithan has a natural awe and adoration toward the city's beauty, and keeps watch over it from a distance when it's not feeding or transporting. The inside of the castle-structure can also be filled with air bubbles to accomodate guests, but this is purely at the discretion of the inhabitants. There are no doors or windows in Eluria, just open entranceways to the inner chambers, though of course these can be blocked for defense. The whole crystal structure acts as a focus of blue mana and magic, and this power is in turn available to anyone who controls the citadel.