Mare Crisium is one of my favorite Moon areas. There is a lot of details inside Crisium, but it is not easy to detect, because it is very fine. High aperture telescopes are needed to spot the small impact craters inside this maria, because its typical lengths are 1 or 2 kilometers wide.
Near Mare Crisium there is another big area called Palus Somni (below), that is visible in this picture made with an amateur telescope. The big and bright crater in the middle is Proclus:
The telescope used is a Celestron Nexstar 5SE and the camera is a Canon EOS 450d (Rebel XSi) DSLR. The picture actually is a mosaic made of two panes.
Computer Physics Lab 