Addis Ababa museum in Meskel Square is a quiet, small museum located just behind the Red Terror Martyrs Memorial museum. This museum has two entrances, one through the Meskel Square area where you have to pay 20 Ethiopian birr to enter the square itself and then 20 more birr to enter the museum (1 united states dollars ~ 100 Ethiopian birr). The other entrance is near the Red Terror Martyrs Memorial museum where you do not have to pay the 20 Ethiopian birr fee to enter the Meskel Square area (but I highly recommend entering this area because it has lots and lots of activities and food cars).

The museum itself is small with rooms where they display actual royal clothes and artifacts with explanations to everything you see. You'll also get to know much of the history of the city of Addis Ababa (lit; the new flower).

After the rooms of the clothes you get to see photos and weapons (guns, sords and shields) used by the Ethiopian army to defend the city against the Italian colonial army. Also you get to contemplate various coin collections and beautiful artifacts.

After completing the inner rooms of the museum, never forget to check out the art gallery upstairs where they host beautiful paintings and sculptures, some of them for sale. There's also another room just above the museum's rooms where they display many paintings given to the museum.

The place has a nice green area in front of the entrance and a very fancy restaurant outside. I'd pay the 20 birr for this area by itself cause it's very green and looks right above Meskel Square.

I'd also pay the 20 birr to experience the Meskel Square area and the various entertaining activities there, especially the rental bicycles.