  LOFAR, the Low Frequency Array, is a next-generation radio telescope that is
being built in Northern Europe and expected to be fully operational at the end
of this decade. It will operate at frequencies from 15 to 240 MHz
(corresponding to wavelengths of 20 to 1.2 m). Its superb sensitivity, high
angular resolution, large field of view and flexible spectroscopic capabilities
will represent a dramatic improvement over previous facilities at these
wavelengths. As such, LOFAR will carry out a broad range of fundamental
astrophysical studies.
  The design of LOFAR has been driven by four fundamental astrophysical
applications: (i) The Epoch of Reionisation, (ii) Extragalactic Surveys and
their exploitation to study the formation and evolution of clusters, galaxies
and black holes, (iii) Transient Sources and their association with high energy
objects such as gamma ray bursts, and (iv) Cosmic Ray showers and their
exploitation to study the origin of ultra-high energy cosmic rays. In this
conference the foreseen LOFAR work on the epoch of reionisation has been
covered by de Bruyn and on cosmic ray showers by Falcke.
  During this contribution we will first present the LOFAR project with an
emphasis on the challenges faced when carrying out sensitive imaging at low
radio frequencies. Subsequently, we will discuss LOFAR's capabilities to survey
the low-frequency radio sky. Main aims for the planned surveys are studies of
z>6 radio galaxies, diffuse emission associated with distant clusters and
starbursting galaxies at z>2.
