The Rock Islands Southern Lagoon holds UNESCO World Heritage status granted in 2012. This marine area contains 445 uninhabited limestone islands formed by volcanic action and coral reef uplift over millions of years. The islands rise from turquoise water as mushroom-shaped formations covered in dense vegetation. Kayak routes thread through narrow channels between islands where mangrove roots grow directly into saltwater. Tour operators in Koror run day trips that typically combine snorkeling stops at multiple sites within the lagoon. The Ngerukewid Islands Wildlife Preserve occupies the northeastern portion of the Rock Islands and prohibits entry to protect nesting seabird colonies and sea turtle beaches.
Jellyfish Lake sits inside one of the Rock Islands and contains millions of golden jellyfish that migrate across the lake daily following sunlight. The jellyfish species Mastigias papua etpisoni evolved in isolation after seawater trapped in the basin approximately 12,000 years ago. Their stinging cells atrophied over generations due to absence of predators. Swimmers enter from a dock after hiking 15 minutes uphill from the boat landing. The lake connects to the ocean through fissures in porous limestone but remains distinct enough to maintain its unique population. Palau temporarily closed Jellyfish Lake in 2016 when jellyfish numbers dropped below measurable levels. The lake reopened in 2018 after the population recovered. Scientists attribute the collapse to El Niño warming and higher rainfall that reduced salinity.
Blue Corner forms where two reef walls meet at a right angle in the open ocean west of Ngemelis Island. Jacques Cousteau filmed here in 1969. Current regularly sweeps nutrients past the corner drawing large pelagic fish. Divers hook themselves to dead coral with reef hooks to hold position in moving water while grey reef sharks, barracuda schools, Napoleon wrasse, and manta rays pass within meters. The dive begins at approximately 30 meters depth. The site requires advanced diving certification because of depth, current strength, and blue water exposure. Operators in Koror run two-tank boat trips to Blue Corner most days when weather permits. The German Channel cuts through the barrier reef on the western side of the Rock Islands. German colonial administrators dynamited this passage in 1900 to allow ships access to phosphate mining operations on Angaur. Manta rays now gather at cleaning stations inside the channel where small wrasse remove parasites. Divers commonly encounter mantas between December and April.
Blue Holes descends through four openings in a shallow reef ceiling that converge into a single chamber at 40 meters depth. Light beams penetrate from the surface holes creating cathedral effects underwater. The chamber exits through an opening in the reef wall at 25 meters where divers emerge onto a sloping wall. This technical dive exceeds recreational depth limits and requires specific gas planning. Chandelier Cave on the Rock Islands contains four air-filled chambers accessible through underwater passages. The first chamber sits at 3 meters depth and each subsequent chamber requires diving deeper and swimming farther. Limestone formations hang from cave ceilings. Tour operators offer guided cave dives for certified divers.
Peleliu island measures approximately 13 square kilometers and lies at the southern edge of Palau. The Battle of Peleliu ran from September to November 1944 when American forces attacked Japanese positions. American commanders predicted the island would fall in four days. Japanese troops under Colonel Nakagawa Kunio fortified over 500 caves in the Umurbrogol mountain ridge with interconnected tunnels and concealed firing positions. The battle lasted 73 days and produced 10,695 American casualties and approximately 10,900 Japanese casualties. Rusted tanks, artillery pieces, and landing craft remain where they were destroyed. The Peace Memorial Park contains monuments erected by both American and Japanese veteran organizations. Visitors walk trails through former battlefields where ammunition casings still surface in the soil. The Thousand Man Cave on Peleliu functioned as a Japanese communications center with carved niches, rooms, and defensive positions visible inside.
The Badrulchau Stone Monoliths stand in northern Babeldaob near Ngarchelong. Fifty-two carved volcanic stones form arrangements with faces carved in ancient Palauan style. Researchers date the monoliths to approximately 161 CE based on carbon dating of charcoal found beneath the stones. Some monoliths exceed 2 meters in height. Local tradition describes them as representations of gods or as boundary markers for a sacred meeting place. Archaeologists have not determined the construction purpose with certainty. The site sits on private land with access requiring permission from the landowner or arrangement through tour operators.
Ngardmau Waterfall drops 20 meters from a cliff in Ngardmau state on Babeldaob. The waterfall runs year-round fed by rainfall in Babeldaob's interior forest. A monorail system installed for tourism ran from the parking area to the waterfall base but ceased operation. Visitors now hike 40 minutes on a muddy trail through forest. The pool at the waterfall base allows swimming. The Compact Road that circles Babeldaob passes near the trail entrance. The United States funded this road network under terms of the Compact of Free Association agreement.
Milky Way lagoon sits within the Rock Islands where white limestone mud accumulates on the bottom in specific cove areas.