The Karakum desert surrounds the oasis of Merv on three sides, and the Murghab river, which feeds the oasis, ends in the sand a little downstream. Talkhatan Baba, a brick mosque and mausoleum in the area of Mary, belongs to the medieval Islamic centuries when Merv was one of the great cities of the world, a Seljuk capital with libraries, observatories and a population that rivalled any in Europe.
It makes more sense seen with the rest of the region. The ancient cities of Merv, listed by UNESCO in 1999, spread across the plain in a series of walled enclosures from different eras, with the mausoleum of Sultan Sanjar, the Seljuk ruler, at the heart of it, and a huge fortress wall of mud brick that has weathered into soft shapes. The Mongols destroyed the city in 1221, and it never recovered, which is why so much is left untouched in the desert.
Practically, Turkmenistan is a difficult country for independent travellers. Visas are hard to obtain, a guide is usually required, and foreign vehicles are subject to heavy paperwork and fees, so most visitors travel with a licensed tour operator. If you can arrange it, the roads in the Mary region are straight and flat, with mile after mile of cotton fields, irrigation canals and desert scrub, and heat that can reach forty-five degrees in summer. Fuel is cheap, but the supply can be uneven, and you should take as much as you can. Bayramaly, a town of about seventy-five thousand, and Murgab, much smaller, have shops and basic services.
Spring and autumn are the only sensible seasons, with March and April bringing green fields and wildflowers on the steppe, and October giving mild days. Bring water, a hat and a lot of patience, and accept the tea that people offer.