Masjid-e-Qiblatain, Madinah, Saudi Arabia
Masjid-e-Qiblatain is one of the most important places in the Islamic history. It is the very same mosque where the Holy Prophet (Peace be Upon Him) received the command from Allah to turn the face towards The Holy Ka'aba in Makkah during Salat. He turned his face there and then, in mid-prayer,from Jerusalem (Masjid-e-Aqsa) towards Makkah facing Bait-ul-Allah.
Allah Says in The Holy Quran, Chapter 2 ( Surah Baqrah) Verse (Ayat) Number 144
"Verily! We have seen the turning of your (Muhammad's SAW) face towards the heaven. Surely, We shall turn you to a Qiblah (prayer direction) that shall please you, so turn your face in the direction of Al-Masjid- Al-Harâm (at Makkah). And wheresoever you people are, turn your faces (in prayer) in that direction. Certainly, the people who were given the Scriptures (i.e. Jews and the Christians) know well that, that (your turning towards the direction of the Ka'bah at Makkah in prayers) is the truth from their Lord. And Allâh is not unaware of what they do."
It is from there on that Muslims around the world face the Holy Ka'aba while praying.