Is the face of a woman considered her Awrah?

If yes, then why do women have to uncover their face in Masjid al-Haram?

The scholars have differed on the issue of whether it is fard or Sunnah for a woman to cover her face. However, all of them have agreed that it is islamically legitimate for a woman to cover her face. The majority is of the opinion that it is a Sunnah for the woman to cover her face whereas; the Hambalis are of the view that it is compulsory for her to cover her face. This issue involves a long debate and my view is that whoever follows the scholars who allow a woman's face to be covered; they can do so because that opinion is based on Sharia proof, and whoever follows the view that it is fard for a woman to cover her face then that opinion is also based on evidence. In this case I cannot impose on anyone any opinion since both positions have evidence. However, it is clear that if a woman covers her face she will be more modest, more protected from fitna etc, especially if she is beautiful.

I suppose that the issue of women uncovering their faces in Masjid al-Haram is linked to ihram issues. Even those who are of the opinion that a woman must cover her face say that while in the state of ihram a woman should not wear the usual naqab which covers the face directly but she should rather wear a "naqab cap" and cover her face in an indirect way.

And Allah knows best.