It is hard to use this improvement effectively. It must be built on a flat Desert tile but blocks that tile from being worked by a Citizen. If you have a desert city with a lot of Hills and you plan to build Petra in it, you should not use this improvement in combination, as the yields from Petra is so much more substantial than yields from the Nazca Line. This improvement should only be used when you have a city settled in sub-optimal desert areas with low Food yield and you tried to rush for Petra but failed, as this improvement can work as the back up plan to keep that city going. Don't go and settle new desert cities just because you are the Suzerain of Nazca when Petra is already built elsewhere, this improvement is not strong or impactful enough to create a bustling desert city for you.
The Nazca lines are huge geoglyphs—figures cut into the earth, created by the Nazca culture that lived in Peru between 500 BCE and 500 CE. Some figures may be older, from the Paracas culture, since the figures follow some of the design motifs found in Paracas textiles. The designs are fragile despite their size, and are made by removing a thin layer of red pebble topsoil to reveal the lighter rock underneath. The Nazca lines are stylized depictions of birds, animals, and human figures. Some of the Nazca lines are simple marks oriented with various celestial landmarks.
The Nazca lines might have been associated with invocations of favorable rainfall from sky deities, but our understanding of Nazca culture is not complete enough to provide anything besides plausible explanations. A variety of less plausible explanations for the lines have been offered, many of which fail tests of parsimony, if not strain credibility to the breaking point.
Changes to the arid desert environment of the Nazca plateau and their popularity as tourist attractions are the biggest threats to the preservation of the Nazca lines. If rainfall patterns change, the lines may literally wash away. If careless tourists continue to damage them, they may disappear beneath the footprints of their admirers.