Through the AZtech Council, I was able to tour the following facility:

http://www.sterlingnetwork.com/

Click on "what we do".  I was in the rooms pictured on the bottom, and 
others.

They're located at 120 E. Van Buren, what used to be an Arizona Republic 
building with printing center.  They've essentially gutted the building 
and designed the best datacenter they could muster from scratch.  The 
datacenter fills both basement levels, a whole downtown one-block 
footprint.  Very impressive.  Not only that, they are aggressively 
giving tours to groups large and small.  They want their biggest market 
to be small and individual businesses.

I'm going to e-mail the person I talked to regarding their tour policy 
and get back here shortly.  To give you an idea: the AZtech Council 
basically held an eveningtime networking meeting in a large lobby area.  
That's the purpose of their organization, networking.  So they provided 
themselves with food, beverage, and booze, they had the first half hour 
to mingle, and then people were just pulled in groups of ten to tour the 
facility.  So chances are we can make a small nerd party out of this, 
(so long as we clean up after ourselves) and just chill out, chat, enjoy 
the whirr of thousands of cooling fans, and think about the many clients 
we can impress with three hops to XO communications and Time Warner.

--Alexander