I didn't bike them myself, but I can tell you about them. Lake Dunstan is a man made lake formed when the Clyde Dam was built. Cromwell is where you hire a bike and start your experience.

Cromwell is a nice wee town with a Heritage Precinct.  Some buildings from the days of old still exist along the waterfront.  In fact there is a Cycle Hire place right  there. Don't know the mans name but we had a chat and he  taught me quite a lot about the history of the area. He is the only one there, so go see him and say Paul sent you for a bike.

There are 5 main trails. 

Smiths Way to Cromwell Heritage Precinct 16km Grade 1

Bannockburn Inlet to Cairnmuir Gully 11.3km Grade 2-3

Cromwell Heritage Precinct to Bannockburn Inlet 7km Grade 2

Halfway Hut to Dunstan Arm Rowing Club 10.7km Grade 2-3

Dunstan Arm Rowing Club to Clyde Heritage Precinct 3.5km Grade 1

On my drive south to Clyde I would watch the cyclists on the other side of the lake riding along the trails and raised cycleways built over the water. Was spectacular and amazed at how many I saw as well.

While in Cromwell visit  Tarras, Bannockburn and Pisa Moorings. Enjoy Central Otago hospitality at its best. 

Be sure to check out the Cromwell Museum and find out about the early gold rush history. the Chinese Miners that arrived in the 1800's. The Maori routes across Central Otago and how they hunted the Giant Moa.

Learn about the miners camps where reportedly 3000 miners lived under canvas at one point, and also the process of building the Clyde Dam, creating Lake Dunstan which included putting a lot of the heritage buildings under water during construction, between 1982 and 1993