The historic Dar al-Hajar is an iconic symbol of Yemen and it's architecture. You can find it prominently displayed on the 500 Yemeni Rial note.
Last month while I was in Sanaa, I took a day trip to Wadi Dahr, a small fertile valley with fruit orchards and qat fields. In Wadi Dahr there is the impressive Dar al-Hajar which Imam Yahia had built in the 1930s as a summer palace. I really enjoyed this excursion and it has been one of the tourist highlights here in Yemen. I posted pics for you to see, click here.
I also youtubed two clips from that weekend:
Bab al-Yemen:
http://www.youtube.com/watch?v=-qvKOa4ExsA
Jambiyya Dancers at Dar al-Hajar: