National Museum Addis Ababa
This Museum has a wide variety of exhibits on three floors, telling stories from pre-historic, ancient to modern times. Of particular interest is the "Lucy" skeleton, which was excavated in 1974 and named after the Beatles song "Lucy in the Sky with Diamonds" is said to be 3.2 million years old.
If you only have time to do one museum in Addis, then the Ethnological Museum inside the main AA University campus at Sidist Kilo is your best choice. It is housed inside the former emperor’s palace and hosts the various tribal people of Ethiopia arranged by life events and the chance to see the King’s throne.
Addis Ababa Holy Trinity Cathedral
Trinity Cathedral is the resting place of the late emperor Haile Selassie. Statues line the church’s walls and fill the surrounding gardens. If you are lucky, you may even experience a mass held on its steps. Plan for an hour or more to appreciate its beauty.