Water is important in Islam.1 In order to perform salah, hold a Qur'an, or circumambulate a holy site, a Muslim must be in a state of purity.2 Most of the time, a ritual cleansing called wudu is required before an act of worship.3 For convenience, Islamic holy sites, like Nizam al-Din's chilla-khana have ablution tanks on site for use by those that intend to worship.
Some mosques, such as the Jama Masjid in Delhi, were designed with a central ablution tank that is sometimes called a fawwara.4
1. Sameh Strauch, comp., Sameh Strauch, trans., Fiqh Course: Tahaarah, Salaah, and Janaa'iz (Riyadh: International Islamic Publishing House, 2003), 21-42.
2. ibid, 47-48.
3. ibid, 38-40
4. Philip Davies, The Penguins Guide to Indian Monuments, vol. 2, Islamic, Rajput, European (London: Penguin Books, 1989), 595.
The Delhi Walla. "City Faith: Hazrat Nizamuddin's Chilla Central Delhi."
Qur'an 5:6. Al-Maidah (The Food).