We study the topological content of the vacuum of SU(2) pure gauge the
ory using lattice simulations. We use a smoothing process based on the
renormalization group equation. This removes short distance fluctuati
ons but preserves long distance structure. The action of the smoothed
configurations is dominated by instantons, but they still show an area
law for Wilson loops with an unchanged string tension. The average ra
dius of an instanton is about 0.2 fm, at a density of about 2 fm(-4).