Every year the Women in Green organization (led by Ruth and Nadia Matar) lead a massive march of Jewish people in a circle around the entire Old City Walls - it is one of the most inspiring of experiences - and often draws in excess of 10,000 participants. Here is a video from the march in 2007. Tisha B'Av (the Ninth of Av) is a full day of mourning and prayer commemorating the destruction of the Jewish Temples on the Har HaBayit (Temple Mounts). It is the only other full day of fasting besides Yom Kippur (the Day of Atonement).