Safa and Marwah are two small hills near the Kaaba. Al-Baqarah 2:158 counts them among "the symbols (sha'a'ir) of Allah" and states that there is no blame on those performing the Hajj or Umrah for walking between them. This rite is called the sa'y.
Islamic tradition explains the sa'y as a remembrance of Hagar running between the two hills in search of water for her infant son Ishmael. The distance between the hills is roughly 450 metres.
Today both hills lie within al-Masjid al-Haram, and the path between them (the Mas'a) has become a multi-storey covered gallery. The marker shows the middle of this gallery.