Old Photo of well of Aab-e-Zamzam
The well of Zamzam is situated within Masjid e Haram in Makkah Mukarma. According to Quran, it sprang as miracle from the dry and barren land of Makkah when Hazrat Hajira (Hagar), wife of Hazrat Ibraheem [Abraham] and mother of Harzat Ismail [Ishmael], ran searching for water as her son Hazrat Ismail fainted with thirst.
Her quest between Safa and Marwa hills was loved by Allah and He generated an everlasting water source there. The running or Hajira between hills of Safa and Marwa also became one of the most important parts of Umra/Hajj, also known as Saee, i.e. walking or running between the hills. Safa and Marwa hills are mentioned in Quran with respect and sings of Allah.
Today everyday hundred of thousands of Muslims pilgrims visit the holy places and perform Saee to remember the miracle of Allah when Hajira at time of troubled times remembered her Lord.
Aab e Zamzam is the holiest water in Islam. Although Prophet advises that one should sit down when drinking water, for Aab e Zamzam one should stand up in respect to drink it.
Also there is Masnoon Dua when drinking Aab e Zamzam, which can be downloaded below: