Down a short forest trail and across a (hopefully) dry stream from Candi Ceto is another temple from the same area, dubbed Candi Kethek. This temple is much more modest than its neighbor. It's really little more than some terraces built into the hillside with a tiny shrine at the top. Several trees still pierce the terraces. For me, the walk was at least as interesting as the temple.
There is no additional entry fee to access Candi Kethek.