The upper town (Citadel) can be visited in 2-3 hours on foot. Essentials: Standard Bastion (panoramic view of cliffs and Sardinia), Genoa Gate (main entrance with drawbridge), Saint-Antoine necropolis (medieval graves carved in the cliff), King of Aragon's Staircase (187 steps carved in the limestone cliff, 70 m descent to the sea, paid access €3), Sainte-Marie Majeure Church (12th-16th centuries, 650 m³ medieval cistern), Podestat House (museum). Free walk on the ramparts.
The port (below in the natural cove) hosts yachts, cruise ships, terrace restaurants. Maximum animation in the evening. Essential cruises: sea caves from the port (1h30, €25-35/person — Sdragonatu cave with its "Napoleon's hat" opening, Saint-Antoine cave, rocky calanques), Lavezzi Islands (€40-55/person return, full day, snorkeling, paradisiacal beaches).
The beaches around Bonifacio: Saint-Antoine (on foot from the town, wild), Cala Longa (5 km, white sand), Piantarella (10 km, kitesurfing, view of Lavezzi), Sperone (8 km, chic, golf), Tonnara (12 km, strong waves). Beyond (30-45 min by car): Palombaggia (Corsica's most iconic, white sand + umbrella pines), Santa Giulia (protected turquoise bay), Rondinara (perfect shell).
The excursions: Sardinia via Bonifacio-Santa Teresa Gallura ferry (1h, €30-50/person return) — possibility of day or several days (Costa Smeralda 50 min away). Sartène (45 min, the "most Corsican of Corsican cities" according to Mérimée, austere granite medieval lanes). Bavella Needles (1h, spectacular D268 road, Hole of the Bomb hike). Porto-Vecchio (30 min, walled old town, lively port, base for Palombaggia).