Yazd was for me an important city along my round trip in Iran. I will not forget this city that quickly. Main area of interest is the old center, with all the very little streets, most of them inaccessible for cars. All the houses are made from clay and you will not find any brick building. With the mosques mixed in between the houses, you never know what to expect around the corner, a dirty and smelly corner, a house, a beautiful mosque, or maybe a moped about to run you over! I stayed in the Silk Road Hostel, well put away from the rush of the main roads. Easy accessible but still in the middle of the atmosphere of the old quarter. A nice place to stay, choose from a private room or a dorm, surrounding the inner garden and the eating and rest area, elevated like a stage. Great atmosphere, good price and very good service. Via the hostel I booked an excursion, visiting three small vilages in the desert. A guide accompanied, shares the theory and historc stories and tells you about what you see and about the region. We vistied Chakchak, Kharanaq and Ardakan.
Also there is the posibility to visit the silent tours, located on the border of the city. At dawn you have a beautiful view over the city, being illuminated by it's street lights. Make sure you decend before dark or bring a proper flash light! It's a steep climb!
Although Yazd is not a beautiful and not a 'well decorated mosque-rich city', it is worth to visit Yazd as it's a complete different experience and very much part of Iran!