El Ciudadano is one of just a handful of good pizza places in Santiago, with oven-fired crusts (as opposed to pre-baked crusts), and has a great, youthful but not juvenile influence. Pizza specialties run to the nouveau, with smoked salmon, etc, but there are some classics on the menu. Salads are plentiful and other menu offerings include Italian, Peruvian and Argentine. Desserts are notable and include a chocolate mousse with hazelnuts. The place itself is wooden and brick, cozy, and always hopping. It's not on the main drag, and the fact that it is always hopping is testament to just how good it is.
Take the green line metro to Santa Isabel and walk a few blocks.