The White City — Elizabeth Bear

For centuries, the White City has graced the banks of the Moskva River. But in the early years of a twentieth century not quite analogous to our own, a creature even more ancient than Moscow's fortress heart has entered its medieval walls.

In the wake of political success and personal loss, the immortal detective Don Sebastien de Ulloa has come to Moscow to choose his path amid the embers of war between England and her American colonies. Accompanied by his court--the forensic sorcerer Lady Abigail Irene and the authoress Phoebe Smith--he seeks nothing but healing and rest.

But Moscow is both jeweled and corrupt, and when you are old there is no place free of ghosts, and Sebastien is far from the most ancient thing in Russia...