There are quite a few places in eastern Europe/central Asia that are on my list to visit, but one place that I never considered until recently was one of the "stans"...Tajikistan. Because of the significant unrest that has taken place in the region over the last few years, it might not be high on your list either. But, one particular item you should not pass up is below:
Pamir Highway - Tajikistan
The highway parallels a number of high mountain ranges, and purportedly follows the paths of the original Silk Routes. If you're feeling adventurous, the path begins in Uzbekistan and follows a 2000km path until reaching Kyrgyzstan.
Getting to the road could take a bit of planning. You're probably best to try and fly into Dushanbe (DYU) (the capital of Tajikistan) and then head out from there. Trekking tours are also available if you need some assistance in planning.