This is the battlefield of the Holy Grail War.
It's not so much a city as it is an island surrounded by sea.
But this may be the whole world—the only abrupt patch of color on the blue planet covering the vast ocean. It is called a colored section because there are various intertwined landscapes here - a majestic volcano made of grey-brown volcanic rocks covered with dark red lava like surging blood, exposed yellow-brown skin, and a vast wilderness slightly decorated with scattered green grass, constantly surging to show long and winding light blue There are rivers and clear and calm lakes of different sizes, mountains that are undulating and covered with various kinds of vegetation like tight veins protruding from the earth, deserts with harsh sunlight, hot sand, and sand dunes that change like the ebb and flow of the tide, stretching glaciers that remain strong all year round, and various human-made buildings that exude simplicity or highlight modern features...
This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.