As I stare at the hole in the cliff side, I can make out broken beer bottles and old candy wrappers that have almost been absorbed by the mountain. “Come on,” my dad says, stepping into the wounded hill. I follow reluctantly, treading gingerly through the thin carpet of trash.

There's still plenty of light in the cave – the entrance is wide and it filters in streams of golden sunlight. It's painted with heavy strokes of mud; the water pooling in the corners is a cloudy white, and the craggy rock walls are dripping with a slimy brown. The floor is encrusted with a decade's worth of trash. We stop at the back wall, flashlights hanging uselessly from our hands.

“Why don't we just climb the ­mountain?” I ask plaintively. “I bet the view's nice.”

“I thought you wanted to see the caves,” Dad says, preoccupied with the sheer stone wall before us. I make no attempt to answer.

Dad sighs, glancing at me. “Let's just give it a chance. If you're not ­having fun in an hour, we'll hike up to the summit.”

I look dubiously at the chimera that is the cave – a twisted mixture of rock and refuse tangled with a lifetime's worth of mud.

“Ah, here,” my father says excitedly. He's found a thin fissure in the back wall, little more than a crack. Darkness pools out of it.

I aim my flashlight at the crevice, but the passage turns almost immediately, so I can't see much. Dad slides through and disappears.

“Widens up over here,” I hear him say. Reluctantly, I squeeze through the scar and press past the darkness.

Echoes are a curious phenomenon. The sound one hears from an echo – whether it's inside an empty room or a cavern under the earth – is just the reflection of what has been said, a mirror of sound. Scientifically speaking, an echo is the reverberation of sound waves off an object. Metaphorically speaking, an echo is a ghost; a repetition of reality.

The argument could be made that all of life is an echo, reverberating from some enormous initial bang. It could be said, not entirely falsely, that we're just repeating things, over and over again, and we'll continue to do so until the end of existence. So, then, what's the point of anything, if everything is simply an echo of something that's ­already happened?

The thin tunnel opens into a cavernous chamber of dark rock. I run my light across the walls. The floor is rock rather than a carpet of trash. Few people have found this place.

“This is cool,” says Dad, his light playing on a fanged stalactite.

It's dark in the cave – the only light comes from our flashlights, which are mediocre at best – but I think I can make out another opening.

“Let's go deeper,” I whisper, shining my light into the new tunnel. It slopes downward sharply and then curves to the right.

We descend.

The air becomes cool and wet, and our beams occasionally highlight patches of twinkling ice on the walls. There are stalactites and stalagmites lining the way, and sometimes clear streaks of crystal dance along with us. We walk for what seems like hours – it could have been days, or years, for all we knew. There is a timeless quality to the air, as if it has never felt the light of day. It seems like we are walking through places where no human has ever trod.

At some point a sound begins to form in the distance, muffled and fragile – like water slapping rocks. The rock and the dark and the sound all press toward us as we go, curtains of a secret heart.

Caves epitomize the power of echoes. Here, sound doesn't act like it does above ground; it seems to come alive. Sound gains certain vibrancy being caged amidst tons of rock, and it can't stay still and die, fading into silence like it does under the sun. It bounces, it resounds, and it reverberates. It explodes. Words said in a cave are captured as if they were ink on a blank page. They linger, fermenting, and sometimes one can stumble across an idea, decayed by time but still faintly coherent, singing through the air in some forgotten cave chamber.

Echoes are not only beasts of sound. They exist as traces of humanity, bits and pieces of lives past. Superficially, they may linger as trash or treasure, but they exist at a much greater depth too. Cave paintings and fire pits – remnants of ancient people – become immortalized in shadowed grottos, an echo of a time otherwise inaccessible.

A single human touch can mar the growth of a stalactite for decades. The flame of a torch can blacken and destroy delicate formations that have grown for thousands of years. A cave is a remarkably fragile place. But they are leaving their own echoes. Echoes of destruction, true, but echoes nonetheless.

A very wise man once said that there is nothing new under the sun. He was right – to a certain extent; with the age of humankind, there aren't any truly original ideas any more. He was also wrong – because an echo is more than its definition, more than a reverberation of sound. It is an encore to nature's symphony.

The tunnel empties into a small circular room that arcs high above our heads. The sound of rushing water is a roar now, bounding and leaping around the room like a caged tiger. I focus my light on the ceiling.

There's a waterfall, crashing down to the slick rock floor and draining in some shadowed pit. My light intertwines with the wreath of spray and beads of shining water seem to float through the air, as if the top of the cave was open to the night sky.

“It's beautiful,” my father says quietly, and his voice is caught on some invisible current, amplified, and thrown around the room, roaring and hissing with the water.