The current issue of Biblical Archaeology Review includes the fascinating firsthand account of how the late Ehud Netzer discovered the tomb of King Herod.  The entire article is available for free online. 

During the 38 years since I began working at Herodium, Herod’s luxurious desert retreat, this architectural masterpiece has yielded many treasures, but none more exciting than the 2007 discovery of Herod’s elusive tomb. Some still question this identification, but more recent discoveries confirm my initial conclusion. Today, I have no doubt of it. […] In the summer of 2006, we turned our attention to the slope of the hill, in the vicinity of the monumental stairway that ran up the hill from Lower Herodium to the palace/fortress of Upper Herodium. We first followed an ancient wall along the northeastern slope, hoping that it would lead us to the burial place (a cave?) at the bottom of the round eastern tower. When no clue was found here, in the spring of 2007 we returned to the vicinity of the monumental stairway and slowly we began to reveal some fragments of reddish stone along the northeastern slope that appeared to be from an elegant sarcophagus. Following these stones, we were finally led to the discovery of Herod’s mausoleum. […] Not long after we announced the discovery of Herod’s tomb in 2007, my good friend British architectural historian David Jacobson expressed his doubts, noting the lack of any inscriptional identification of the remains. Since then, we have finished digging the whole area around the monument, exposing more of its architectural elements. This has enabled our capable architect-archaeologist Rachel Chachy to draw a detailed reconstruction of the mausoleum. If the same remains had been found near Jerusalem, it might have been risky to identify the monument as belonging to Herod. But this is Herodium, Herod’s personal monument, named for himself—indeed, the only one. And Josephus has told us Herod was buried here. There can be little question who was buried here. The absence of any inscription should not detract from this conclusion. […] Duane Roller, professor emeritus at the Ohio State University, is another doubter. A distinguished Roman historian, Roller concedes that the tomb we have found belonged to someone of noble lineage, but he remains convinced that Herod lies at the solid base of the east tower on the summit.

The well-illustrated article is a must-read before your next visit.  If you want to read more about Herod and his construction projects, I would highly recommend Herod: King of the Jews and Friend of the Romans, by Peter Richardson as well as The Architecture of Herod, the Great Builder, by Ehud Netzer.