In Sydney, Australia, there's this network of alleys that run through the city.

Narrow lanes, some built on paths that predate the city.

But over the years, as Sydney's gotten bigger and denser, these alleys have become crowded

with air conditioners, garage entrances, and garbage bins.

If you round the corner by the recital hall in downtown Sydney, you'll come to Angel Place.

And the back of a building architect's probably figured no one would see.

It's one of these old narrow lanes dotted with exhaust vents.

But coming around that corner, you'll start to hear something.

Something that takes you back to the old Sydney.

Bird songs.

They're delicate, melodic, maybe even a bit haunting.

Above you, 120 bird cages hang suspended over the narrow alley,

silhouette it against the sky, and swaying gently in the breeze.

Some are simple wire cubes, others more ornate.

In the bird songs, they're coming from every direction.

But the cages, they're all empty.

The birds you hear aren't here,

at least not anymore.

I'm Tracy Samuelson, and this is Atlas Obscura,

a celebration of the world's strange, incredible, and wondrous places.

Today, we visit Forgotten Songs,

and our installation that reminds Sydney residents of the birds that have disappeared

...