  We consider Ricci flow on two classes of nilpotent Lie groups that generalize
the three-dimensional Heisenberg group: the higher-dimensional classical
Heisenberg groups, and the groups of real unitriangular matrices. Each group is
known to admit a Ricci soliton, but we construct them \textit{explicitly} on
each group. In the first case, this is done using Lott's blowdown method,
whereby we demonstrate convergence of arbitrary diagonal metrics to the
solitons. In the second case, which is more complicated, we obtain the solitons
using a suitable ansatz.
