is a quintessential example of a walled plain. Measuring 96km in diameter and 800m in depth, its ancient form can be located east of 300km ‘the sea that has become known’. It is not the clearest of lunar craters, its ringed plain defined by a gently raised rim to the west, appearing broken in form to and 48km to the south. This pair are ancient too, but presumably younger than Fra Mauro as their rims appear to bulge into Fra Mauro's boundary, inverting the curve of the walled plain's rim. This suggests they were formed after Fra Mauro and overlay its edge.
