This interesting 9.5 mile route runs from Dalkeith to Penicuik. From the Dalkeith end it can be started from either just off the Sheriffhall Roundabout (Edinburgh Bypass) on the A68 or from just outside Dalkeith town centre. If starting from Dalkeith, the path entrance is between the town centre and the Eskbank roundabout - just past the Condor self drive garage. This is signed as part of the Number 1 National Cycle Route.
The path goes via Bonnyrigg and alongside Roslin Glen Country Park and past Auchendinny before emerging in Penicuik. There are quite a few possible on/off points along the way. From the Dalkeith end the surface starts as high quality tarmac following an old railway. However after Bonnyrigg it becomes narrow and muddy, before turning into shale. This section is not good for roadbikes.
Starting from the A68 the path goes under a bridge under the road and continues pretty much flat for a few hundred yards. You then come to a bridge over a spectacular gorge, along which flows the River Esk. Immediately after the bridge is a junction - turn right - continuing straight on will take you into Dalkeith.
Further along there is a short section of rough track, before more good tarmac, takes you along to Bonnyrigg. Somewhere around here the Number 73 National Cycle Route is joined. After this the quality of surface deteriorates and at one point it is a narrow muddy path. There are a couple of tunnels to go through as well, which adds to the fun.
It's possible to escape just before the end with a steep climb up Kirkhill. Unfortunately the ride back into town along the main road isn't all that much fun, so it may be better just to retrace one's steps.