About 4km north of town is Khao Luang Cave, a dramatic stalactite-stuffed cavern that's one of Thailand’s most impressive cave shrines, and a favourite of King Rama IV when he was a monk. Accessed via steep stairs, it's lit by a heavenly glow every morning (clouds permitting) when sunbeams filter in through the natural skylight.
Things change throughout the year, but the sun shower generally happens between 9am and noon; earlier is better. And note that you have to be standing in the right spot to see it. From February to April the light illuminates the main Buddha image.
Deeper in the cave there are more chambers and shrines, although the back exit is no longer in use. The story is that Rama IV built the stone gate that separates the main chamber from the others as a security measure for a couple who once lived in the cave.
You can walk up the steep hill to the entrance, or ride in a truck for 15B. You'll meet many brazen monkeys looking for handouts here, though they don't go inside the cave. There are also sometimes guides asking to join you. They're not necessary, and a tip will be expected.