I'm going into first year at McMaster for the IBEHS program and I was just wondering about the underground tunnels. Which residences connect and do they all go to the centro building? Are there underground tunnels connected to Hedden Hall?

I never heard of any tunnels at all going to the residences from anywhere. What a security nightmare and legal liability that would be!

You can travel underground/indoors through University Hall/Gilmour/Chester New/Togo/KTH/the business building and the student centre. And you can travel indoors from Burke to General Science. That's all I know.

Oh, there are also utility tunnels connecting most if not all buildings, but the general public can't get into them. Rumours back in the day were there was also an underground nuclear bombshelter on campus, but again you can't get into it.

There is also a basement route from ABB to Thode lib.
ABB has an above ground tunnel to JHE