The Gran Teatro, Havana's stunning Old World opera house. Breathtaking. That's the word that keeps cropping up when I try to describe Havana, after traveling there twice in June. Our first trip was leading the 5-day "Sketch Cuba" tour, which is described in several posts below. For the second trip, my wife Patti and I traveled alone to retrieve my "Hemingway's Cuba" exhibition of sketches from Finca Vigia (Hemingway's home outside Havana, now a national museum) and bring it back to the U.S…