Toronto's "Mystery Tunnel" is a Spider Hole

http://upload.wikimedia.org/wikipedia/en/thumb/5/59/Spider_hole.png/250px-Spider_hole.png


This mystery tunnel is anything but mysterious. It's an ambush position known in military terms as a spider hole.

http://www.cbc.ca/news/canada/toronto/mystery-tunnel-found-near-pan-am-games-venue-1.2968367

Any kind of meth lab or grow op would need an exhaust port for the chemicals or generator so you could breath or keep the generator running. Exhaust would draw attention.

It's not a tunnel because it doesn't go anywhere.

This article disproves that the tunnel was the work of engineering students.
http://www.ctvnews.ca/canada/toronto-bunker-builder-lucky-it-didn-t-collapse-expert-says-1.2254522
Even first year engineering students can do a force body diagram and figure out they need lateral support.


http://en.wikipedia.org/wiki/Spider_hole

It looks like it can hold a 10 people. Plus supplies for the wait until ambush.

Here's how one might use it. Build a spider hole in a secure area long before surveillance. Wait till the event to load it with weapons and ammo. Attackers go into the spider hole 3 days or so before event security tightens up, then they wait until the right moment to burst out and attack.

You dig it in the winter when no one is around, then it gets hidden by vegetation in the spring.

If you want to hide from detection, you make sure it does not collapse under the ground weight and thawing conditions. You build it with a structure to make sure the space won't collapse on you.  You truck away the dirt, hide the entrance in some trees, and camoflage the ingress path.

If you find the people that made this spider hole, be very cautious they are probably well-armed and expecting that knock on the door.