The Sunnyside Museum on Avondale Road holds the most interesting collection in town: artefacts from Pacific Islands missions, early printing equipment used to produce Adventist literature, and domestic objects from the settlement's founding years. It also has material on Cooranbong's Aboriginal history and the Awabakal people who lived on the lakeshore before European settlement.
The building itself is a tidy Victorian weatherboard house, preserved largely as it was in the late 19th century. The museum is small and can be done in about an hour, but gives a genuine sense of the idealism and ambition that drove the community to establish itself in this then-remote valley. Check opening times before visiting — it keeps irregular hours and is often run by volunteers.