. It is a longkang I came by one day and I decided to go down to have a look. Contrary to what many people believe, it's pretty clean down there aside from spiders and wasps 
. The breeze down there is amazingly cool too 
It's very dark but your eye gets adjusted to the darkness to enough to see the way.
From one end it is very dark as the light is blocked by many trees from the outside.
But from the other end, you can see the whole tunnel as there is more light coming in.
There's a ladder in the mid section of the canal
A Swallow's nest, who wants bird's nest soup?
Lots of wasp nest attached to the ceiling and walls
The underground canal connects a pond and a lake. On one side there's a shallow pond with lots of small fishes in it. It's a perfect nursery for juvenile fishes, I only saw a haruan and some barbs though. On the lake side which is deeper, I can see more fishes like cichlids and tomans.
The shallow pond
The lake
I find that tomans do not like shallow waters, as I've observed in many ponds including this one. Haruans on the other hand, are very well adapted to just a few inches of water. They will charge up waterways that are very shallow and narrow to find new places to dwell in; and sometimes cascading waterways that seems impossible to accomplish.
