A novel way of delivering high-speed internet via beams of light through the air has successfully transmitted data across the Congo River.
Project Taara is one of Alphabet X's (formerly Google X) so-called moonshot ideas.
It grew out of Project Loon, a broadband project using balloons in the stratosphere, since shut down.
The latest experiment means that a "particularly stubborn connectivity gap" between the two African cities - Brazzaville in the Republic of the Congo and Kinshasa in the Democratic Republic of Congo - has been filled, said the team in a blog.
The cities lie only three miles apart but connecting them is tricky because traditional cable has to be routed around the river, making broadband prices five times more expensive.