Eco-trekking in Rumassala jungles will take you closer to the nature, It's said that the wide and varied vegitation in this area is really a dropped piece of Himalayas that was being ferried by Hanuman vide Ramayanaya epic.
There are many foot paths and likelyhood of your getting lost is minimal.
You can also go thru Rumassala to get to the small beach on the eastern flank of the Galle harbour called Jungle Beach, here the corals are of a high biodiversity.
If you go into the bush just above the beach there are lots of locals in village houses. They will sometimes invite you for a cup of tee. I saw a old blacksmith with furnace like in the 1900's Britain, and more wildlife inc large Monitor Lizards and Monkeys
The Tsunami had taken everyone's belonging with their broken houses and furniture and left a big mess. The sea had eroded about 30 feet of the beach. The locals say the first row of illegal beach huts had been washed away. The hotels on the landside of the road were now facing the sea. Although most had been damaged, the owners probably consider it a blessing in disguise since this rare tsunami had improved their location on the bay.