  We give an improved lower bound of 10/3 on the competitive ratio for the
exploration of an undirected, edge-weighted graph with a single agent that
needs to return to the starting location after visiting all vertices. We assume
that the agent has full knowledge of all edges incident to visited vertices,
and, in particular, vertices have unique identifiers. Our bound improves a
lower bound of 2.5 by Dobrev et al. [SIROCCO'12] and also holds for planar
graphs, where it complements an upper bound of 16 by Kalyanasundaram and
Pruhs[TCS'94]. The question whether a constant competitive ratio can be
achieved in general remains open.
