  We solve a $1+5$-dimensional cylindrical gravitational-wave solution of the
Einstein equation, in which there are two curvature singularities. Then we show
that one of the curvature singularities can be removed by an extension of the
spacetime. The result exemplifies that the curvature singularity is not always
a spacetime singularity; in other words, the curvature singularity cannot serve
as a criterion for spacetime singularities.
