This is a wonderful flower. I am sure it belongs to the Cactus. The plant is rather unwieldy. A beautiful white lilly is the flower. What's unique about it is that it blooms only in the night and stays only for that night. It's accompanied by a  mild, sweet fragrance.
Believe it's been  the subject for many poets...the transcience of beauty!
Flowers from May to August.
Also called Brahma Kamal and Nishagandhi...see a lot of them in B'lore.During the  flowering season, the papers always carry the news about whose plant had the maximum flowers.There's also the superstition that the one who sees it bloomed ,is in for prosperity....Well, my take is that its sight is such a memorable one,that in itself is luck and prosperity!
My trials at capturing it on camera: