Tombs have always been excellent places for archaeologists to learn about a people. Also, the customs of some societies dictated that the person be buried with personal items, household effects, treasures and sometimes even servents. These remains can be studied to learn about the culture of that group. Unfortunately many tombs were robbed in ancient or recent history, depriving scientists of the valuable information they contained. In a few cases however, like the tomb of King Tut in Egypt and the Lords of Siapan in Peru, the graves have been excavated mostly intact.
Scientists have a number of different methods to determine a likely place to start an excavation.
Even some buildings thousands of years old can still be visible if they were built well with stone, like Egypt's Great Pyramid. Low, regularly-shaped hills or mounds of earth can indicate a place where people have lived for a long time, perhaps a city. As parts of the city are torn down and rebuilt over time, the old rubble is often used as fill or foundation for new structures. Over hundreds and hundred of years this can create a layer effect. As scientists dig down through the mound, they see various layers for each rebuilding of the city.