The Red Pyramid, also called the North Pyramid, is the largest of the three major pyramids located at the Dahshur necropolis. Named for the rusty reddish hue of its stones, it is also the third largest Egyptian pyramid, after those of Khufu and Khafra at Giza. At the time of its completion, it was the tallest man-made structure in the world. It is also believed to be the world’s first successful attempt at constructing a “true” smooth-sided pyramid. Local residents refer to the Red Pyramid as el-haram el-watwat, meaning the Bat Pyramid.

en.wikipedia.org/wiki/Red_Pyramid