FREE PARKING: It is better to park at 5th Avenue North Garage, as it is Seattle Center’s newer garage and if a user enters at its Republican Street entrance it is only a short walk to Seattle Opera. Although the Mercer Street Garage is an option too (but construction nearby)

Enter the parking structure at take ticket so that gate will lift.
Redeem free parking coupon at drive
At exit gate, insert ticket (given at entry) 
Machine will tell you amount to pay
Instead of paying, enter coupon and gate will lift allowing exit
 
There are currently no blood drives scheduled.