Safely felling elevated wooden structure?
On a day with calm winds, cut 3/4 through each leg, near the ground, with the cuts all starting from the same compass direction. Post an observer to watch for movement in the upper portion of the structure and warn the sawyer. 
Pull the structure down with human, animal, or machine power using suitably strong and long straps in the opposite direction as the cuts. The legs will crack together. A crowd-pleasing crash will result.