A Convict's Subterrane

The day starts out normally enough.
Sun shinning. Birds chirping. All the makings of a beautiful day.
Then we look down.
This is not a normal day.
Beneath us a rivulet of fetid water pools against walls of red brick, graffiti and grime. Pouring into a deep trench, it's then whisked away into the seedy underbelly of a convict's city.
One look between friends is all we need to agree on exploration. Glancing around we see our opportunity. The wire fence behind the Men's Gallery has been jimmied open, allowing access into the drains below. A shimmy down the bank and two sets of dirty knees later we land on squalid ground.
Looking back, I'm surprised to see the water tumbling in from a natural stream. It bubbles, cascading through mossy rocks and gnarled trees. The water is clear here, even crystal. It stands stark against the urban subterrane ahead.
The walls are high and Hobart's buildings perch upon them, held together by street art and age.
It is here we leave the daylight.
Into the underground we go.
Firstly we notice the air. It doesn't smell, but is thick and muggy. My skin attempts to crawl with the change of density, but instead drowns in its new layer of clam. We head towards the city center, the walls showing murmurs of the metropolis above as drain pipes jut from the brickwork, dripping down to a steady stream and the echoes of voices fill our chamber like the ghosts of prisoners past.
For 15 minutes we wander, peering down offshoots to the unknown and trying not to slip on the sludge.
Then, turning a corner, the tunnel becomes lit.
No longer dark nor dank, it has opened into a subterranean gallery. The walls are covered in the art of tunnel punks gone by, from the beautiful to the brash, an exhibition of works from artists monikered Curly or NoreLord.
We stay here for hours and night has fallen by the time we move on. As we search for an exit, the tunnel promptly ends and we find ourselves under the stars with a clear and easy access to the street.
Hearing a splash we pause in our departure.
"It's a fish!
No.
It's a Platypus.
Startled by our torchlight, he pulls an awkward three-point-turn and rushes off into the darkness. We follow him for a while but he escapes our gaze.
This is not the last we see of him, as we have returned many times. It seems that when darkness arrives, so does our platypus.
So my question is this: with a chance to see the underground, modern art and such a rare and beautiful creature;
Why would you see Hobart any other way?