All that we see or seem

The Stanley Hotel near Boulder, Colorado is haunted. Or so everyone says. The young writer who stayed there one night in 1974 wasn't terribly impressed with the stories - he was used to scary stories. But a haunted hotel gets quite a bit spookier when you're its only guests. The writer says: "They were just getting ready to close for the season, and we found ourselves the only guests in the place - with all those long, empty corridors... I dreamed of my three-year-old son running through the corridors, looking back over his shoulder, eyes wide, screaming." The writer woke in a cold sweat, smoked a cigarette, and then set to work writing The Shining, about a family alone in an old Colorado hotel for the winter, being chased through the halls by every sort of ghost and demon. Stephen King published the novel in 1977 and Stanley Kubrick made it into a movie in 1980. The room King stayed in that night was, of course, 217.
It's certainly not hard to believe that writer H.P. Lovecraft was a man haunted by vivid nightmares his entire life. He wrote of these nightmares in letters to friends - in one of which he says

As I was drawn into the abyss I emitted a resounding shriek, and the picture ceased. I was in great pain - forehead pounding and ears ringing - but I had only one automatic impulse - to write.

His work does have a very dreamlike feel to it - unspeakable words, impossible shapes, the "sensation of the presence of the hideous unknown," as he put it. 
When Paul McCartney woke up with a hauntingly beautiful tune in his head, he was desperate to know where it had come from. It was such a lovely melody, and he thought. "I couldn't have written it because I dreamt it." He played the tune to just about everyone he knew to ask if they recognized it before finally accepting that in fact, the tune was original. 
Paul didn't know what lyrics to put to the music, so he hastily threw in the placeholder title Scrambled Eggs. Today we know the song as Yesterday. 

A Dream Within a Dream
Edgar Allan Poe

Take this kiss upon the brow!
And, in parting from you now,
Thus much let me avow —
You are not wrong, who deem
That my days have been a dream;
Yet if hope has flown away
In a night, or in a day,
In a vision, or in none,
Is it therefore the less gone? 
All that we see or seem
Is but a dream within a dream.

I stand amid the roar
Of a surf-tormented shore,
And I hold within my hand
Grains of the golden sand —
How few! yet how they creep
Through my fingers to the deep,
While I weep — while I weep!
O God! Can I not grasp
Them with a tighter clasp?
O God! can I not save
One from the pitiless wave?
Is all that we see or seem

But a dream within a dream?

A set for a nightmare-fueled existentialist play...
Actually, inside the LaSalle Theater, Cleveland, Ohio.
My "This Place Matters" photo is the outside of the same theater.

Sources: Wikipedia.org, LorePodcast.com, http://www.philhine.org.uk/, http://www.beatlesbible.com