The Rajathans were a species once native to the planet Rajatha Prime. Their civilization died out in approximately the 4th century. The Rajathan civilization was a pre-industrial society that built large cities with monumental structures. Their constructs included ziggurats which featured ceremonial entrances to heaven and the underworld, as the Rajathans were "pathologically non-judgmental" they gave both entrances equal status. Inside these entrances were chambers containing sarcophaguses and other decorative items. (TNG comic: "Captain's Pleasure")
Dates given are based on Jean-Luc Picard's claim that no person had walked the halls of Rajathan ruins in two millennia prior to 2368. The Rajathan level of architecture and art would seem to be roughly comparable to the Maya of Earth.