http://www.fountainplace.com/pages/tunnelmap.asp
I used to work in One Dallas Centre (#16) when mom worked at Energy Plaza (#11) and we both used banks and restaurants in and just off of the underground. My bank and my usual lunch spot were at 1700 Pacific (#22). In addition, going by way of the Jackson Street Parking Garage (#24) would get me a lot closer to the library before I had to leave air conditioning, and leaving the car in a $2 surface lot all day (or riding DART from a free parking area well off downtown to the St Paul Station and entering the underground at ODC to walk the last half-mile or so...it says a lot about Dallas that public transit service to the main library sucks so badly) rather than driving six or seven blocks saved a good bit of money.
There's a lot more space that could be used down there, but Johnny America seems a bit pessimistic unless it's been going downhill a lot worse since I was there. (roughly 1997-2000, with occasional ventures into downtown through 2002)
