  We present a detailed study of the transport properties of a superconducting
Pb/Cu microdot with a 2x2 antidot cluster. The superconducting-normal (S/N)
phase boundary, critical currents and current-voltage characteristics of this
structure have been measured. The S/N phase boundary as a function of field B
(T_c(B)) reveals an oscillatory structure caused by the limited number of
possible vortex configurations which can be realized in these small clusters of
pinning centres (antidots). We have analyzed the stability of these
configurations and discussed the possible dissipation mechanisms using the
critical current (J_c(B)) and voltage-current (V(I)) characteristics data. A
comparison of the experimental data of T_c(B) and J_c(B) with calculations in
the London limit of the Ginzburg-Landau theory confirms that vortices can
indeed be pinned by the antidots forming a cluster and that the ground-state
configurations of the vortices are noticeably modified by sending current
through the structure. The possibility of generating phase-slips as well as
motion of the vortices in the 2x2 antidot cluster has also been discussed.
