Solutions of Einstein's equations representing spacetimes with closed timelike curves (CTC) are commonly dismissed as unrealistic. Recently I published approximate solutions, containing CTC, which refer to ordinary sources. In this paper I present an exact vacuum solution, asymptotically flat, which contains CTC. It represents a massless rotating rod of finite length, and I give reasons why addition of mass would not abolish the CTC. I suggest that there is now an urgent need for a realistic physical interpretation of CTC in general relativity.