This is whichever Doctor you'd like it to be. Which means, of course, that it's each of him/them. Rated K. Advanced critique encouraged.
He could hop in the TARDIS and in a matter of (relative) moments arrive at the end of the life of the very stone upon which he stood. Stone is solid, massive and immutable and, inevitably, doomed.
Or he could go back to when the roaring river that formed the gorge below was only a rivulet, before the steady but inexorable wear of its waters had eaten through miles of hardy-seeming rock, before the layers became exposed to the baking heat of the desert sun and the darkling chill of night air.
The contours of this land had formed over an immensely long period of physical abuse from wind and sun and stone and sand. It was a harsh landscape, still and sharp, gritty and uncompromising.
Perhaps that's why he'd come: to see himself reflected in earthy reds and browns.
It always came back to the Earth, didn't it? Why did he feel compelled to run here, of all places within his reach? Why was he calling it 'the Earth,' instead of simply 'Earth', a treatment above that earned by Mars or Barcelona or Dulkis? There were so many reminders of pain here, each little grain of his memory chafing in the turbulent wind. He'd been exiled to this insignificant – no, that's not right – to this mostly harmless little planet. He'd saved it countless times. Here, he'd met villains and would-be conquerors, intergalactic babysitters and personal heroes. On Earth unfolded innumerable acts: kindnesses unthanked and devastating horrors alike. It was here his granddaughter stayed behind, here the TARDIS chameleon circuit chose to break down and he subsequently chose not to fix it, instead opting to carry around that little physical bit of Earth culture to every place he visited.
And it was here, on Earth, that he'd fallen in love.
Countless times. He loved as only a centuries-old Time Lord could, alternately burning hot and cold, fire and ice.
Not in this exact place, of course. But he envisioned himself coming back here, for solace. Wind and rock were twisted into more spectacular formations on other planets in other galaxies but there remained only the singular Earth in his eyes.
Well, until there was a New Earth, anyway.
He found that during his musing he had wandered to the edge of the great ravine and stood there, toes of his trainers nosing into the empty air. He stood for a long, unmeasured moment. The walls of the canyon were rosy in the waning light of the setting sun. Vertical layers of dull brown and deeper, rusty red were thrown into relief, oddly reminiscent of a cake. If all the birthday cakes of the Earth were stacked one upon another, would they reach the depth of this canyon? Possibly. Here, one could at a glance see far back in time, to the forevers ago when silt and mud settled out of the thick, brackish soup of an ancient shallow sea. Slowly, imperceptibly settling and shifting, debris had compacted over the years into layer after layer of rock, memories of moments on Earth made solid, not dead but frozen. Sedimentary sentiments.
If prompted (but by whom? They were all gone, they always left in the end), he would have said he had no idea how long he stood there, peering down over his shoes into the crevasse without seeing it at all. He would have claimed he hadn't felt he passage of time, so deep were his thoughts.
It would have been a lie. He knew, he always knew. He knew exactly how many years and days - minutes and seconds and breaths and heartbeats - separated one anguished instant from the next. Somehow he felt every distinct inch and light-year and yet continued to exist, if not to endure. Knowing defined him, formed the very core of his being.
The Doctor wondered, not for the first time, just how slowly a man could collapse.
It was a long way down. He'd fallen to his death once before. Not a pleasant way to go. But that was only the briefest of memories, a single flicker in an ongoing slide show of lives long past yet vivid.
It was a sound, faint but distinct, that finally pulled his surface thoughts to this particular here and now of the desert southwest. His gaze focused and pointed, returning from the abyss and finally alighting on the source of the subtle rustling sound.
"Oh, hello," he murmured, barely a breath.
The sun had long ago set. The impersonal light of the solitary gibbous moon was not filtered by the cool, clear air as it hung over the place the ravine tapered to a point on the horizon. Distances were deceptive in the desert; it was as if one could see forever... and remember it, too.
The sound was a comforting white noise: the bristles of an impossibly twisted and gnarled pine, bent and folded in the wind but clinging stubbornly to the dry, red rock. Roots grasping the flaking stone, this pine was short and stunted but, he knew, very, very old.
He walked over and placed his rough hand on the weathered trunk. It was warm and felt of coarse sandpaper. Whole sections of bark had been parted from the tree by the savages of time and weather, beast and ill fortune. Yet there was a meager flow of life locked inside the sun-bleached wood, twining its way past deadened sections, still striving for the sun. He could feel all this and more.
"Hello," he said again.
The bristlecone pine, a small part of his mind intoned in its melded visual-numerical-slightly-psychic-verbal way, can survive to be thousands of years old, yet lives and grows only in the harshest and most arid of conditions. Maturation and development are slow. The outlining figure of the pine is often influenced by its resistance against and its being shaped or molded by the prevailing winds of the immediate surroundings. Similar species include the Ilkx of tropical Raglor, the ice plants of Nikk, the ocean-floor frond beds of the Southern Seas of Clorf, as well as the Limbor peoples of Nil, second moon of Korr in the Red System and...
And it went on. A mental index of lifeforms, each more ancient and sessile than the next. Having followed the pathway of slow but steady development, such life was rarely active or adventurous. Bound to rooting structures or clasping anchors or frozen stilts, these individuals sat and watched and simply lived, motionless and inert, for countless centuries: the evolutionary slow road, reincarnated a million complex ways throughout the stars.
He had once visited the Limbor race, curious to observe an advanced lifeform that outlived him and his kind by, quite literally, millennia. He'd asked them about the quiet life, but ironically became so bored in waiting for a response (communication from one cell-body to the next is necessarily slow among the Limbor) that he'd actually skipped off to a more exciting planet before they'd articulated their response.
Quite frankly, he wasn't sure he wanted an answer. It was one thing to gaze upon the countless – well, not really countless, not for him – stars as they twinkled into view in a perfect, purple desert sky and imagine watching the peaceful view unfold before him every night into infinity, each time just a bit different. But in the end he knew he would grow restless. It did no good to stand on very high ravine ledges and think to oneself all day, just waiting for a random gust of wind to push in the wrong (right) direction.
The Doctor turned away from the bristlecone. Perhaps he'd come back and they'd meet once more as old friends with long memories. Perhaps there would be new growth in this harsh desert yet.
**Author's Note: A single, Earthly bristlecone pine can live up to 5,000 years, all without ever leaving its little patch of dry, barren land. Chew on that, angsty spaceman.