The walls around the patio at the back of the owl house are decorated with relief figures from the Rubaiyat of Omar Khayyam.
The two figures pouring wine into a cup come from quatrain 46:
So when at last the Angel of the darker drink
If Darkness finds you by the river-brink,
And, proffering his Cup, invites your Soul
Forth to your lips to quaff it - do not drink.

