A good 50km from Yazd lies the Sar Yazd castle, slightly outside the village with the same name. Apparently, it is rather close to the well known Zein-o-din Caravansarai, but we never made it there. The fortress is built from adobe and used to have a moat.
Since there are few tourists, it sometimes can be tricky to find the person with the key. So best to inform at the tourist office in Yazd or go there with a guide (or else you will just be able to see the high walls). We crossed the moat and went inside, following our guide Mohammed. Some adobe structures are in a terrible state and can be rather unsafe, but not this fortress.
The original castle traces back to the 7th century, but different sections have been repaired and updated during different eras. After you have crossed the moat, you will find yourself in an actual maze. The castle has three floors, and you need to know your way around to find the narrow, hidden, entrances to the next floor up. These small openings made it almost impossible for intruders to enter. The narrow alleys are so small that only one person can pass at a time.
The primary usage of the Sar Yazd castle was grains and food storage, which was of essential value in that era. In addition to foods, people hid their valuables such as gold and jewellery in one of the over 450 chambers when the city was under assault.
If you can find the way, you can go all the way up to the top floor of the tallest tower. From there we had a great view of the surrounding desert and the mountains including the 4055-metre Shirkuh, a high peak in the central part of Iran about 40 kilometres west of the castle.
To get to the castle, you could either take a taxi, but I would recommend a guide as he or she could call in advance to make sure that someone is available to open the massive door and help you to navigate the maze inside the castle.