Sailing to Sarantium — Guy Gavriel Kay

Crispin is a mosaicist, a layer of bright tiles. Still grieving for the family he lost to the plague, he lives only for his arcane craft. But an imperial summons from Valerius the Trakesian to Sarantium, the most magnificent place in the world, is difficult to resist.

In a world half-wild and tangled with magic, a journey to Sarantium means a walk into destiny. Bearing with him a deadly secret and a Queen's seductive promise, guarded only by his own wits and a talisman from an alchemist's treasury, Crispin sets out for the fabled city. Along the way he will encounter a great beast from the mythic past, and in robbing the zubir of its prize he wins a woman's devotion and a man's loyalty -- and loses a gift he didn't know he had until it was gone.

Once in this city ruled by intrigue and violence, he must find his own source of power. Struggling to deal with the dangers and seductive lures of the men and women around him, Crispin does discover it, in a most unusual place -- high on the scaffolding of the greatest artwork ever imagined....