The limestone that walls the Kilim River is roughly 450 million years old — Setul Formation rock, among the oldest exposed carbonate in Southeast Asia. It predates the mangroves growing at its feet by an almost unimaginable margin. The park covers around 100 square kilometres of the island's northeast, where the Kilim, Kisap and Air Hangat rivers empty into the Andaman Sea. UNESCO recognised Langkawi as a Global Geopark in 2007, the first such designation in Southeast Asia, and Kilim remains its most visited component. A langkawi mangrove tour kilim geoforest park route threads between karst towers, tidal channels and caves whose ceilings are hung with stalactites. Gua Kelawar — the Bat Cave — shelters roundleaf and fruit bats within a boardwalked limestone hollow. Nearby, Gua Buaya takes its name from crocodiles that once patrolled the estuary. What holds the system together is Rhizophora and Avicennia: red and grey mangrove species whose stilt roots trap sediment, buffer storm surge and nurse juvenile fish. The Kedah state government gazetted the area for protection, and boat operators are licensed through the Kilim River Tourism Jetty at Mukim Kampung Kilim. Brahminy kites and white-bellied sea eagles are the signature raptors; long-tailed macaques work the mudflats at low tide, prising open shellfish. Mudskippers, archerfish, monitor lizards and horseshoe crabs complete a food web that ecologists study as a reference site for tropical estuarine health. Entry to the park itself costs 0 MYR, with fees applying only to individual boat tours and site attractions — a structure that keeps the geopark public while funding the operators who run it. Floating fish farms anchored midstream sell fresh catch and stock stingray and horseshoe crab for close viewing. Beyond them the channel narrows towards the Andaman, where the Hole in the Wall passage cuts through a limestone ridge into a sheltered lagoon. Guided langkawi mangrove tour kilim geoforest park tickets typically cover this stretch by boat or kayak. Conservation pressure is real. Wildlife feeding, once routine on eagle-watching runs, has been curtailed to protect natural foraging behaviour, and operators increasingly favour slower, quieter routes. The park matters less as scenery than as evidence: a legible record of Cambrian seabeds, monsoon hydrology and living forest occupying the same frame. Few places compress geological time and biological present so tightly, which is why the Kilim estuary anchors any serious itinerary through Langkawi Geopark.