  Based on the relativistic quark model and the infinitesimally shifted
Gaussian basis function method, we investigate the mass spectra of double
bottom baryons systematically. In the $\rho$-mode which appears lower in energy
than the other excited modes, we obtain the allowed quantum states and perform
a systematic study of the mass spectra of the $\Xi_{bb}$ and $\Omega_{bb}$
families. We analyze the root mean square radii and quark radial probability
density distributions to deeply understand the structure of the heavy baryons.
Meanwhile, the mass spectra allow us to successfully construct the Regge
trajectories in the $(J,M^{2})$ plane. We also predict the masses of the ground
states of double bottom baryons and discuss the differences between the
structures of our spectra and those from other theoretical methods. At last,
the shell structure of the double bottom baryon spectra is shown, from which
one could get a bird's-eye view of the mass spectra.
