  The scheme of simultaneous multiple pulse focusing on one spot naturally
arises from the structural features of projected new laser systems, such as ELI
and HiPER. It is shown that the multiple pulse configuration is beneficial for
observing $e^+e^-$ pair production from vacuum under the action of sufficiently
strong electromagnetic fields. The field of the focused pulses is described
using a realistic three-dimensional model based on an exact solution of the
Maxwell equations. The $e^+e^-$ pair production threshold in terms of
electromagnetic field energy can be substantially lowered if, instead of one or
even two colliding pulses, multiple pulses focused on one spot are used. The
multiple pulse interaction geometry gives rise to subwavelength field features
in the focal region. These features result in the production of extremely short
$e^+e^-$ bunches.
