Beaver Tunnel
Okay, right off I'll admit this is a misnomer.  These are, in fact, nutria living in the water outside this tunnel, not beaver.  However, when you first see them, they look like beavers with their little flat faces.  The tail, obviously, should be the giveaway, but they scooted the moment they saw us.

At any rate, Dani and I visited this tunnel a month before this trip.  Unfortunately, it was shortly after a heavy rain, so it made it very difficult to get into.  However, I went on in and photographed the hell out of the place and had a grand old time while Dani stayed topside and walked her dog.  Well, that was great and all, but the pictures were worthless.  I mean, there was absolutely no frame of reference to any of them, so you, the viewer, couldn't tell whether a tunnel was inches across or the size of a cathedral.

As you will see, this happens to be a kickass tunnel, so I brought Dani back in and we took a new set of photos and even videotaped a lot of the trip.  What's more, we checked out number of side tunnels and even went more than twice as far this time as I had before.  This system is huge!

Here's a view from the outside.  The two tunnels are to the left, mostly obscured by the branches of the rude tree that stepped into the frame.

Just to the right of center is a hole in the side of the canal where the nutria hide out. 

Note that this picture was taken on our first visit here when the water was quite a bit higher.  Typically a little more of the hole is exposed.
We had to lower ourselves down the sides of the canal with a rope tied around the pipe above.
This is the entrance to one side of the tunnel.  The other tunnel is a round culvert that runs parallel to and then meets back up with this one further upstream.

Incidentally, "Night Run" refers to an event by Candlelighters Childhood Cancer Foundation, not anything related to urban exploration.
This is one of a number of access points to manholes at street level, just to show you how far below the surface this system is at this point.

I would liked to have been able to get GPS coordinates at each of these points, but the holes in the manhole cover are too small for the signal to reach the receiver.
This is a side tunnel that I looked into briefly last time but never fully explored. 

Dani suggested we check it out while we were there, and I'm glad she did considering we spent three hours of walking, climbing, and crouching through the rest of this system.  I would have been too tired to visit this area on the way back.
We entered from the right as viewed from this angle, and I went on ahead to see whether anything was worth checking out.

In this image I am standing (err, crouching) just beyond a pile of concrete from a cave-in.  Naturally, these are rare occurrences, so don't worry so much about us already!
Thankfully, the tunnel grew larger and eventually was high enough to stand up in.  This was surprising, given that most tunnels grow ever smaller as you work your way upstream.

At this point, this section branched off in two directions.

I think Dani was rolling up her pants in this picture.  I don't know why exactly.
This is the tunnel to the left.  In a bizarre repeat of the Matrix Reloaded tunnel, this one also concluded inexplicably in a dead end.  However, this time it appeared that mud had been piled in from the other side.  Too bad I didn't bring my shovel!

And, not surprisingly, the other, smaller tunnel on the opposite branch was similarly blocked.
We returned to the main tunnel and continued on.  The rule I try to follow in order to keep from getting lost is to always take the larger tunnel as I explore.  Those tend to be more fun besides.

An unusual feature of this system is that it branched like this at several points, only to rejoin a few hundred feet later.  However, these tunnels do not run strictly parallel, but instead wind far away, possibly so as to bring each closer to areas with a number of smaller inlets.
Note that the architecture continually reverses itself throughout this place.  We alternate between smooth walled culverts and medieval style archways.  I cannot explain this.
Here was another surprise!  Believe it or not, this turtle (I guess it was the same anyway) was here the last time I passed through.  He is about 12 inches long. 

The last time, once I got past him, he took off for downstream, but this time he remained calm and held his ground even after we passed him.  I can't even begin to guess as what there is to eat down here!
On to the next part