Goat Island, west of the Harbour Bridge, has been a shipyard, quarantine station and gunpowder depot in its previous lives. Three-hour heritage tours depart at 10.30am on Sundays from Cadman's Cottage; bookings essential. On the last Sunday of the month the boat departs the island 45 minutes later (and costs $3 more), allowing extra island time for a picnic lunch (bring your own).