There are two tees for #21, the first is to the left of, and visible from the #20 basket. The more challenging tee for #21 is uphill beside the building to your right.
From the long (upper) tee, you'll need a drive you can get safely around the corner of the building, but one that won't roll away downhill toward the pond. Follow that with an approach shot that gets you up the hill through the sparse trees for your par putt.
Oh, and par (3) here is doing well!