Blessed with a breathtaking location, Nagasaki is strung together on a long series of hillocks in a scenic valley that follows the arms of the Urakami River down into a gentle harbor. Unlike Hiroshima, the city was left with no suitably intact reminders of the atomic bombing, and perhaps for this reason, there were apparently no compunctions about rebuilding the town right up to the edge of a tiny ground-zero circle with a stark steel monument at its center. Although almost all buildings are relatively new, Nagasaki's international history shows through, from lively and compact Chinatown to the European-style mansions and Catholic churches on the hillsides.
The city isn't small, but it occupies a long winding valley, so you can experience it in manageable increments. Similarities with San Francisco are frequently noted. The comparison is not far off, though the posters advertising whale-bacon and manga remind you of where you are. Most of the interesting sights, restaurants, and shopping areas are south of Nagasaki Station, but the Peace Park and the Atomic Bomb Museum are to the north, 10 to 15 minutes by streetcar or taxi.