Banganga is an ancient water tank in South Mumbai.

Here's more info from http://en.wikipedia.org/wiki/Banganga

According to local legend, it sprang forth when the Hindu god Ram, the exiled hero of the epic Ramayana, stopped at the spot five thousand years ago in search of his kidnapped wife Sita. As the legend goes, overcome with fatigue and thirst, Rama asked his brother Lakshmana to bring him some water. Laxman instantly shot an arrow into the ground, and water gushed forth from the ground, creating a tributary of the Ganges, which flows over a thousand miles away, hence its name, Banganga, the 'Ganga' created out on a 'Baan' (Arrow).

The tank today is a rectangular pool structure surrounded by steps on all four sides. At the entrance are two pillars in which oil lamps called diyas were lit in ancient times. The tank, as well as the main Walkeshwar Temple and the Parshuram Temple belong to the Goud Saraswat Temple Trust, which once owned most of the property in the complex. Many Goud Saraswat Brahmin families to date reside in the complex. The tank is spring fed and so its water remains sweet, despite being located only a few dozen meters away from the sea. It is cleaned and spruced up each year, for the annual 'Banganga Festival', of Music organised by the Maharashtra Tourism Development Corporation (MTDC), which takes place here in every January, and now has become an important event in the cultural calendar of the city.

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