This cache is part of the "Get your kicks!" caching trail along Derby's radial bike route, Route 66!
As this bike path is very well maintained by Sustrans, I would strongly recommend completing the route by bike.
All caches are accessible on foot too though 
This cache is located just above Route 66 as it passes through the tunnel.
You are looking for a unique micro cache. The cache is clearly marked so don't touch anything you are not certain about.
The best place to park if doing this as a C&D is in the giant supermarket. You cant miss it!