Umit Berksoy's tiny atelier, hidden away in Istanbul's Grand Bazaar since 1968, has been discovered by the world's jewelry connoisseurs. The queen of Spain commissioned Byzantine-style earrings in 24-karat gold. Sharon Stone chose a platinum dragonfly in diamonds and cabochon rubies—one of the brooches he custom-crafts in gold, silver, or platinum in the shape of bees, starfish, lizards, frogs, often with large, unusual stones (from $1,500). Other treasures: stunning Russian antique jewelry. At Inciciler Sokak, Nos. 2-4-6; 90-212-522-3391.