Good route Sliven to Elena, via Vratnik col.
I was a bit worried re this stage, but it actually is great but hard work.
Follow the #53 road north from Sliven (poorly signed, follow the river). It quickly enters big hills via a pretty wooded valley. And we found good smooth surfaces, reasonable graded and almost no traffic. There is a weight limit so no juggernauts.
But it does go on! Allow 4 hrs if loaded up, as there is one ridge top, a fairly big drop, then the 2nd climb to Vratnik at 1097m. Total ascent so far 1050m?
Springs for refreshment. No cafe.
The descent is steep and long; surface not so good north of col.
At Stara reka there is a shop, no cafe.
On pleasantly through rural villages, some up and down, surface improves.
Finally into Elena town which has a hotel etc. We measured 78 km, total ascent c. 1300 m, 8 hours Inc. stops.