Three Pennsylvania Turnpike tunnels were bypassed in the late 1960s when the highway was modernized.

One, Laurel Hill, has been turned into a high-tech race car testing facility.

The other two were supposed to be part of a pedestrian and bicycle trail that was never completed. They remain unofficially open to the public.

There's been a lot of interest in those tunnels, so here's what you need to know, what we've had so far and what more we have coming on them:

COMING TUESDAY:

Off the visit to the Pennsylvania Turnpike tunnels by state legislators on Thursday, a look at the tunnels and their long-term future.

SO FAR: