(1) There is no record that King Solomon and the Queen of Sheba (her name was probably not Sheba) ever had a child or any relationship other than a conversation in the course of a formal state visit.
It is not attested in the Scriptures.
It is a legend among Ethiopians.
(2) The presence of the Ark in Ethiopia is also a folk legend which does not have a scrap of documentary or physical evidence - despite the efforts of many archaeologists to track it.
(3) According to the Ethiopians it is not in a monastery, but in a church.
(4) That church, the Chapel of the Tablet of Our Lady Maryam of Zion, is not located on an island in a lake but in the town of Aksum, right in the downtown area.
The only people who are allowed into the sanctuary are male Ethiopian Orthodox believers. There has never been any external confirmation of whether it's there, and probably most guests to the sanctuary never even see it.
very interesting. never knew all that extra stuff, and the history channel never mentioned it, either.