Huon and Far South: See
While it depends on whether the sky wants to have it or decide to not, the Southern Lights is a common sight in this region of Tasmania, provided that you are not viewing the lights in a location affected by light pollution (so not Huonville or even small towns like Franklin or Geeveston). This page has an aurora predictor for the next upcoming three calendar days, but it's not 100 per cent accurate; BOM's SWS may also be of some use.
While this region isn't particularly for glacial lakes (the Highland Lakes region is, though), there are a few near-pristine lakes in Hartz Mountains National Park, most of which have good walking trails; Lake Esperance has it a step further with a boardwalk.
For those interested in caves, Hastings Caves State Reserve contains the largest dolomite cave in Australia, which contains more flowstones, straws, and shawls than other Australian caves (good for photography). Close to the caves is a thermal hot spring, perfect for a cold Tasmanian summer morning.
To learn about the region's timber industry, The Wooden Boat Centre in Franklin has a collection of locally-manufactured wooden boats alongside the Huon River. While the timber industry has mostly died out today, Huon pines were among one of the popular species of trees for timber harvesters during the 20th century.