Merv, Turkmenistan. Existing from the 3rd millennium BC until the 18th Century and now in ruins, this city - reputedly the largest on earth at one time, with a population of over 500,000 - was once a key centre of Islamic science and arts. Now long-abandoned, it is still redolent of those busier times.

Konye Urgench, in north-eastern Turkmenistan, hosts some fascinating remnants of Khwarazmian architecture.