In this work we study the equatorial causal geodesics of the Taub-NUT (TN) space-time in comparison with \emph{ mass-less} TN space-time. We emphasized both on the null circular geodesics and time-like circular geodesics. From the effective potential diagram of null and time-like geodesics, we differentiate the geodesics structure between TN spacetime and mass-less TN space-time. It has been shown that there is a key role of the NUT parameter to changes the shape of pattern of the potential well in the NUT spacetime in comparison with \emph{ mass-less} NUT space-time. We compared the ISCO (innermost stable circular orbit), MBCO (marginally bound circular orbit) and CPO (circular photon orbit) of the said space-time with graphically in comparison with mass-less cases. Moreover, we compute the radius of ISCO, MBCO and CPO for \emph{ extreme} TN black hole (BH). Interestingly, we show that these \emph{ three radii} coincides with the Killing horizon i.e. the null geodesic generators of the horizon. Finally in Appendix-A, we compute the center-of-mass (CM) energy for TN BH and mass-less TN BH. We show that in both cases the CM energy is finite. For \emph{ extreme} NUT BH, we have found that the diverging nature of CM energy. \emph{ First}, we have observed that a non-asymptotic flat, spherically symmetric and stationary extreme BH is showing such feature.
Categories: gr-qc