The best place to start you adventure on the Valley Trail at night is at the Whistler Golf Club - Directly across highway 99 from the whistler conference centre. 

From the parking lot (pay attention to pay parking times), walk west towards the clubhouse, where you will find the entrance to the Valley trail. Although the trail goes for many kilometres in either direction, this particular stretch between the golf club and Blueberry hill is a magically lit walk through old growth forest. 

Usually plowed in the winter, you can do this in good shoes, unless there is heavy snow. 

Don't forget your camera!