The Black Mountain Tower or now called Telstra Tower is located at the top of Black Mountian in the Black Mountain Reserve.
The Telstra Tower is a communication tower though it also has an observation desk which is open to the public 365 days a year between 9am - 10pm (even open of Xmas Day and Good Friday). The views over Canberra are the best there are both for viewing during the day or going up the tower in the evening to see the city of Canberra all lit up. The tower stands 195.2 meters above Black Mountain, The public observation deck is located around half way up this height but as it is ontop of the mountain it is 870 meters above sea level.
There are 360 degree views as you can walk right around the observation deck to look over Canberra city with impressive views of all of Lake Burley Griffin. In other directions the views look out to Woden, Mount Stromlo, Mount Painter, Belconnen, Gungahlin and Mount Ainslie.
For more details for Telstra Tower at Black Mountain.