Use Duval as a spine, not a boundary
Duval runs between the Gulf and Atlantic sides of the island and passes through several different environments. Step onto cross streets and parallel streets and the atmosphere changes quickly. Wooden houses, shaded porches, gardens, churches, small businesses, and civic buildings allow the city to speak in something other than a barroom voice.
Follow the waterfront
The Historic Seaport connects the city's maritime past with present-day working boats, restaurants, galleries, and excursion departures. Mallory Square contains layers of shipping, communication, military, art, and tourism history that are easy to overlook during the sunset crowd.
Look for the people who shaped the city
Bahama Village, Cuban cigar history, the San Carlos Institute, the city cemetery, local folk art, and literary sites provide a fuller account than a celebrity-only itinerary. The cemetery's records alone reflect Bahamian mariners, Cuban cigar makers, military veterans, Black residents, Jewish residents, wealthy families, and poor families sharing the island's history.
Then get beyond the streets
The surrounding water is part of Key West, not an optional backdrop. The island grew through that water and remains physically vulnerable to it. A responsible boat, snorkel, fishing, sailing, paddling, or wildlife experience can explain the destination more clearly than another hour of shopping.