We investigate the future determination of the CKM matrix using theoretically clean quantities, like $B(K^+\to��^+��\bar��)$, $B(K_L\to��^0��\bar��)$ or $\sin 2��$, $\sin 2��$ as extracted from CP violation studies in $B$ physics. The theoretical status of $K\to����\bar��$ is briefly reviewed and their phenomenological potential is compared with that of CP asymmetries in $B$ decays. We stress the unique opportunities provided by measuring the CP violating rare decay $K_L\to��^0��\bar��$. It is pointed out that this mode is likely to offer the most precise determination of ${\rm Im}V^*_{ts}V_{td}$ and the Jarlskog parameter $J_{CP}$, the invariant measure of CP violation in the Standard Model.

LaTeX, 15 pages, 2 figures