cereus flower

I have a big old cactus thats pretty bland most of the time, except when it blooms. It's a night bloomer that only stays open one night. So I miss it sometimes, but when I do catch it blooming, it's quite the flower. It's about 5 inches of white petals across on a long tube about 7 inches long. Just this delicate flower. I have made several mandala from this flower, but really like this one. It almost looks like clouds this time. I liked the hint of the center square, also.