The Meredith graph is a quartic nonhamiltonian graph on 70 nodes and 140 edges that is a counterexample to the conjecture that every 4-regular 4-connected graph is Hamiltonian.
It is implemented in the Wolfram Language as GraphData["MeredithGraph"].
The Meredith graph has chromatic number 3 and edge chromatic number 5.
The plots above show the adjacency, incidence, and distance matrices of the graph.