Ive heard there is a tunnel from the hospital to MDCL , where exactly is this located? thanks

I know of a bridge... not sure about a tunnel. Maybe there is one!

If you go to the health sci library, go upstairs, turn left and walk down the hallway, you will eventually see a sign that says MDCL bridge.

You can reach the bridge from the second floor of either MDCL, or HSC. If you're coming from MDCL, take the elevators on the first floor next to the main entrance to the second floor. Once you come out, you will be right in front of the chemical biology laboratory. Go right and walk straight to the end of the hall. Take another right and keep walking... the bridge will be on your left side. There is also a bridge connecting the two buildings on the fourth floor of MDCL. Hope this helps.

In case you don't know there is also another bridge; connecting HSL to LSB. If you climb the stairs to HSL, once you reach the top go left, and then go left again at the first turn and you should find the door there.

What's the first rule of the underground tunnels at McMaster, again?

Second rule of the underground tunnels at McMaster?