In the Alfama district, narrow, twisting streets and soaring flights of steps wind up to an imposing castle on one of the city's highest hills. This is a grand place to get your bearings and take in supreme views. Because its foundation is dense bedrock, the district—a jumble of whitewashed houses with flower-laden balconies and red-tile roofs—has mostly survived the wear and tear of the ages, including the great 1755 earthquake.
The timeless alleys and squares have a notoriously confusing layout, but the Alfama is relatively compact, and you'll keep circling back to the same buildings and streets. Once rather run-down, it now throngs with tourists as cool bars, boutique hotels, and restaurants are moving in.