Ko Mae Ko Mother Island is a must to visit. Here, an emerald seawater lake in the middle of the island is encircled on all sides by limestone cliffs, but linked by an underground tunnel connecting with the sea. Reaching the lake entails a strenuous climb of 40 minutes or so, but is rewarded with a spectacular view across the whole park.
Rather, the climb is up a series of staircases wonderfully combined into the natural landscape of the karst, threading through a narrow opening in the rock face at one point, and entailing minimum exertion if you pace yourself and are in decent physical shape. The final series of steps is a bit steep and caution should be exercised when descending the steps, but the entire trip up and down would not take 40 minutes unless you stopped and enjoyed the spectacular Emerald Lagoon, as the locals call this trapped sea-lake inside the collapsed island, for 20 minutes or so from the lookout point at the very top.
