Take a day trip to Kharanaq (must visit place – one of the last remaining mud cities of Iran), Chak Chak (a plgrimage center for Zoroastrians, rather underwhelming) and Narin Castle, Meybod (probably the oldest bulding in Iran, dating back to atleast 2000 BC). Usually visited together, these places take around 7 or 8 hours including travel. The Tourist Information office near Alexander's Prison offers this tour for IRR 1,500,000 per head. Alternatively, you can hire a taxi for the same (cheaper if you are 4 people or more).
Take an evening trip to the lake (Jafar's Pond) in the nearby desert (highly recommended). There you can walk in the desert to the lake, go dune bashing, ride quad bikes and/or camel. All inclusive, it is about IRR 1,450,000. The Tourist Information office near Alexander's Prison offers this tour, as does a small office located between the Silk Road Gallery and Cafe Irani.
Walk around in the historic neighborhoods and relax in the parks.
Hike up in the beautiful mountains of Yazd and enjoy a spectacular view of the city.
Varzesh-e Pahlavani, (near Amir Chaqmaq Square). 18:30. Watch the fascinating performance of Persian ancient “heroic sport” which is a combination of martial arts, strength training and aerobic to the rhythm of traditional Persian singing and drumming. The sports centre (which alone is a fascinating building) is located in one of the side streets near Amir Chaqmaq Square. Ask around and everybody will show you the direction. It's a popular show among tourists and the rooms fills up with them so come earlier to secure a place. If you're into this kind of performances / sport, come even earlier (at 5pm) to watch the warm-up without any other tourists present 40000.