The Koʻolau Mountains are a volcanic mountain range located on the island of Oʻahu in the state of Hawaii. Stretching approximately 30 miles, they rise sharply from the eastern coast, creating a dramatic landscape. The mountains are known for their lush vegetation, steep cliffs, and numerous waterfalls, making them a popular destination for hikers and nature enthusiasts. The range was formed by volcanic activity around 2.5 million years ago and is part of the larger Hawaiian-Emperor seamount chain. The Koʻolau region is also home to unique ecosystems and endemic species, contributing to its ecological significance.