  A spacetime consisting of parallel electric/magnetic fields held together by
its own gravity in the presence of a cosmological constant $\Lambda$ is derived
as a limit of the de Sitter/anti-de Sitter C-metric. The limiting procedure is
similar to the $\Lambda=0$ case where the Melvin universe is derived from the
C-metric. Under an appropriate coordinate transformation, we show that this
solution is equivalent to the solution obtained by Astorino. Some physical and
geometrical properties of the solution are studied, as well as its geodesics.
For $\Lambda<0$, the solution is asymptotically locally anti-de Sitter, and can
be derived as a double-Wick rotation of a charged anti-de Sitter black hole
with a planar horizon.
