Mt Eccles National Park and Lake Surprise. Mt Eccles is approximately 30 minutes from Port Fairy. You may see Eastern Grey Kangaroos, Koalas, Sugar Gliders, Yellow-bellied Gliders, Possums, Quolls, Brush-tailed Phascogales, Dusky Antechinus and Swamp Antechinus and over 68 species of recorded birdlife. Walking trails, picnic grounds, swimming in Lake Surprise (the crater of the volcano), camping and the Byaduk Caves (one of the most extensive lava caves in Australia) are all features of the park.
Park entry is free.
Google Map directions here