  Single crystals of Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$, $x<0.37$, have been grown
and characterized by structural, magnetic and transport measurements. These
measurements show that the structural/magnetic phase transition found in pure
BaFe$_2$As$_2$ at 134 K is suppressed monotonically by Ru doping, but, unlike
doping with TM=Co, Ni, Cu, Rh or Pd, the coupled transition seen in the parent
compound does not detectably split into two separate ones. Superconductivity is
stabilized at low temperatures for $x>0.2$ and continues through the highest
doping levels we report. The superconducting region is dome like, with maximum
T$_c$ ($\sim16.5$ K) found around $x\sim 0.29$. A phase diagram of temperature
versus doping, based on electrical transport and magnetization measurements,
has been constructed and compared to those of the
Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM=Co, Ni, Rh, Pd) series as well as to the
temperature-pressure phase diagram for pure BaFe$_2$As$_2$. Suppression of the
structural/magnetic phase transition as well as the appearance of
superconductivity is much more gradual in Ru doping, as compared to Co, Ni, Rh
and Pd doping, and appears to have more in common with BaFe$_2$As$_2$ tuned
with pressure; by plotting $T_S/T_m$ and $T_c$ as a function of changes in unit
cell dimensions, we find that changed in the $c/a$ ratio, rather than changes
in $c$, $a$ or V, unify the $T(p)$ and $T(x)$ phase diagrams for BaFe$_2$As$_2$
and Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ respectively.
