This is one among the most completed structure.  It is believed that originally there was a lingam in the garbagriham and this mandapam was then the Arjuna mandapam.  The lingam was lost & the public replaced it with a Ganesha idol with permission from the Collector in the nineteenth century and henceforth it came to be known as the Ganesha Ratham.  There are two pillars and two half pillars (pilasters) with a seated lion as base, a cylindrical carved portion above the lions head, a sixteen sided portion above that and a bracket.  There are two dwarapalakas at the two extreme ends of the ratha. 

There are several ganas carved on the roof, just below the kapotam.  On the kapotam, there are kudus (circular arches) with the carving of a face in each kudu.  Just above the kudus are a row of yalis.  There is a highly carved top for the mandapam in two layers with a single cellular shrine at the top. 

There is a single cellular mini shrine on the roof - sala (wagon head) at the top.  If the body of the mandapam is rectangular, the roof is normally a sala.