Umm el-Qa'ab is the early royal cemetery of Abydos, where tombs associated with Egypt's first dynasties lie out in the desert. It is not a showy monument, and casual visitors may find it hard to read without a guide, but historically it is one of the most important places in Egypt.
The site became wrapped into the cult of Osiris, which is why Abydos drew pilgrims for so long. If you visit, treat it as an archaeological landscape rather than a single sight: distance, orientation, and silence are part of the experience.