Fractal basin boundaries provide an important means of characterizing
chaotic systems. We apply these ideas to general relativity, where oth
er properties such as Lyapunov exponents are difficult to define in an
observer independent manner. Here we discuss the difficulties in desc
ribing chaotic systems in general relativity and investigate the motio
n of particles in two and three black hole spacetimes. We show that th
e dynamics is chaotic by exhibiting the basins of attraction of the bl
ack holes which have fractal boundaries. Overcoming problems of princi
ple as well as numerical difficulties, we evaluate Lyapunov exponents
numerically and find that some trajectories have a positive exponent.