Concierge.com's insider take:
Every era of Palermo's complex history has been stamped into the stone, making the city a palimpsest of Arabic, Norman, and Baroque architecture. Nowhere is this more apparent than in the Santa Maria Assunta cathedral in Quattro Canti (the city's central "Four Corners" crossroads). The cathedral incorporates a Norman apse, Gothic portico, neoclassical interior, Baroque cupola, and even remnants of the tenth-century mosque that predated it.
The magnificent Capella Palatina, in the Palazzo dei Normanni, is the city's most gorgeous example of Norman architecture. Within the Norman royal palazzo, this mid-12th-century chapel glitters with mosaics, gold, polished stone, and colored glass; its painted, coffered ceiling depicts scenes from the Old Testament. The nearby 12th-century ruined monastery of San Giovanni degli Eremiti, with its Norman bell tower and Islamic cupolas, is a lovely confluence of architectural styles—and surrounded by subtropical gardens of pomegranate and jasmine. And if you can't make it to the ruins of Selinunte, the city's Museo Archeologico, housed in a 16th-century convent, contains some beautiful carvings and statuary from the site (www.regione.sicilia.it).
If you're after a full sensory experience in a spectacular historic building, visit the 1897 Teatro Massimo, Italy's largest theater, for an operatic performance of Verdi or Puccini (www.teatromassimo.it). Another kind of sensory overload can be had at the casbah-like Vucciria Market, which fills the side streets of Piazza San Domenico every day but Sunday. Here, locals can be seen haggling with vendors over every imaginable kind of produce: cuts of meat, fish, octopus, giant piles of fruits, vegetables, and herbs. It's not a relaxing place to wander (in Italian, vucciria means "clamor" or "hubbub," which is right on the money), but it's unforgettable.