The Gulf of Cagliari has been called the Golfo degli Angeli since the medieval period, after a legend in which angels dropped a stone into the sea to trap a fallen devil — the stone became the Sella del Diavolo, the saddle-shaped headland that still closes the bay's eastern edge. That headland is limestone, raised from a Miocene seabed, and it carries the ruins of a Punic sanctuary and a Roman cistern on its flat summit. Beneath it lies Poetto, an eight-kilometre strand of pale sand. Phoenician traders anchored in these waters by the eighth century BCE. Carthage followed, then Rome, then Pisa, whose merchants fortified the Castello district on the hill above the harbour in the thirteenth century. The tuna fleets of Capo Carbonara and the coral boats of Alghero worked the same coast. Every subsequent power — Aragonese, Spanish, Savoyard — read the gulf the same way: a deep, sheltered basin, open south, guarded by two promontories. A cagliari boat tour private charter today follows sea roads that predate the city's walls. What the water conceals matters as much as what borders it. Posidonia oceanica meadows carpet the seabed from Calamosca westward, oxygenating the shallows and holding the sand in place; the plant is protected across the Mediterranean and gives the gulf its particular green-into-cobalt gradation. Flamingos feed in the Molentargius and Santa Gilla lagoons that flank the harbour, some three thousand pairs nesting within sight of apartment blocks. Grouper, octopus and salema shelter in the rock terraces off Cala Fighera. The limestone continues underwater as fissures and small caves, which is why visibility here is measured in tens of metres rather than metres. The modern marina sits at Via Roma, along the Bastione arcades, where the Aragonese quay once stood. From it, the coastline reads as a single geological sentence: Sella del Diavolo, Calamosca, Cala Regina, then the long white shelf toward Chia. Private boat tours in Cagliari — catamaran, speedboat or self-drive dinghy — exist because that coast is legible only from the water; the coast road turns inland and misses it entirely. Skippers hold local licences and know which coves take the mistral and which stay glassy. Gulf of Angels sailing has become the city's defining excursion for that reason. A cagliari boat tour private itinerary is less a sightseeing route than a reading of stone, seagrass and wind, assembled over three thousand years of anchorage.