What is Al Masjid Al Haram? I remember it being mentioned several times in the Quran (I don't remember which Surah).
Al-Masjid Al-Haram (The Sacred Mosque) is the mosque surrounding Al-Bayt Al-Haram (The Sacred House, i.e. Kaaba) in Mecca, Saudi Arabia. It is in that direction that all Muslims are commanded to face when they perform their daily salat.
More details available at the Wikipedia page: Masjid al-Haram