At the base of the Taka Mountains is this spectacular mosque, centre of the Khatmiyya or Khatmiyah Sufi sect. It's a lovely mudbrick building with a pointed octagonal minaret and a photogenic arcade of columns in the main prayer hall. Non-Muslims are quite welcome to take a peek about. Afterwards have a little scramble around the bizarre peaks of the mountains. It's about 4km southeast of Kassala's centre.
Get there by taxior minibus.