What Admirals Arch is
Admirals Arch is a natural rock cavern carved into the cliff at Cape du Couedic, the south-western tip of Kangaroo Island. The arch frames an Australian fur seal colony hauled out on the rocks below. The boardwalk drops down from the carpark, winds along the cliff face, and ends at a lookout platform inside the cavern itself. Standing on it you are framed by the arch, with the fur seals on the boulders directly underneath and the Southern Ocean breaking around them.
The arch was wave-cut over thousands of years. Stalactites hang from the inside of the cavern roof. The cliffs around it are limestone laid down on top of the older granite that runs under the rest of the west end. Most visitors describe the moment of stepping into the cavern as the surprise of the day, because the boardwalk hides what is coming until you are inside it.
The fur seals
The colony is Australian fur seals. They are not sea lions. The Australian sea lions live at Seal Bay on the south coast and are a different species in a different setting. Fur seals are smaller, darker, with a more pointed snout and longer flippers, and they prefer rocky cliffs and offshore islets to sandy beaches. The Admirals Arch colony lives here year-round, hauled out on the boulders at the base of the cliff between hunting trips.
Best viewing is in seal pup season, October to December, when the pups are most active and the colony is at its most photogenic. Numbers fluctuate. On any given day a quiet count will turn up 20 to 50 visible, and a busy day during pup season will run well into the hundreds. You will hear them before you see them: the colony is loud, especially at low tide.
Getting there
Admirals Arch is inside Flinders Chase National Park, which requires a vehicle entry pass from the Park Visitor Centre. Cards are accepted. Pay before you drive in.
From Kingscote it is around 115 km and 1 hour 50 minutes via the South Coast Road. From the Flinders Chase Visitor Centre at the western end of the park it is 15 km on sealed road, about 18 minutes. The road into the carpark is sealed all the way. From the carpark a 400 m boardwalk descends to the lookout inside the cavern. The return walk is uphill and includes stairs, which is the part that catches some visitors out.
The Cape du Couedic Lighthouse
The Cape du Couedic Lighthouse sits on the headland 200 metres above the arch. There is a walk-up viewing platform at the base, and no interior tours run regularly. Built in 1909, it is the southernmost lighthouse in South Australia and has been guiding ships around the bottom of Australia for over a century. The keepers cottages next to it have been restored and are available as accommodation through SA Parks. The clifftop walk between the lighthouse and the arch carpark is short and worth the detour for the southern view.
When to go
Late afternoon for the best lighting in the cavern. The arch opens to the south-west, so the late sun reaches into the cavern and lights up both the rock and the fur seals on the boulders below. Combine that with a low tide for the most fur seals visible on the lower rocks, and ideally seal pup season (October to December) for activity, and you have the best version of the visit. Mid-day in summer the cavern is in flat light and the carpark is full of bus tours.
The walk down is exposed. In summer the wind off the Southern Ocean can be cold even at 28-degree air temperatures, and a windbreaker is worth carrying. Winter is dramatic but cold and very windy, and the boardwalk handles the conditions fine. The arch is open year-round.
Safety
The boardwalk is sealed and fully fenced from end to end. Stay on it. The cliff edge above the arch is unfenced and the drop is around 100 metres straight down to the rocks where the fur seals live. Keep kids in arms reach and away from any unmarked clifftop edges. The boardwalk handles wet weather without trouble, but stairs in the rain are stairs in the rain, so take it slow on the way back up.
Pairs with
Admirals Arch pairs naturally with Remarkable Rocks, 10 minutes east on the same loop road. Most guests do them as a pair on the same Flinders Chase day, with Admirals Arch in the afternoon when the fur seals are most active and Remarkable Rocks at sunset for the golden light on the granite. Cape du Couedic Lighthouse is on the same headland above the arch and adds another 30 minutes to the visit. The full west-end loop is comfortable inside half a day if you start early from Kingscote.