What is this exactly? It could have been made 
with fluorescent green on a landscape photo.

 But it’s really part of the landscape.

It just took a bit longer.

Artist Stuart Williams talks about his luminous grid project, installed in 1993, which was the size of 8 football fields and used 1,680 T-8 fluorescent lamps:

Approximately 20,000 person hours of labor were expended. It took a team
of 12 people, one month to pre-assemble various electrical components
off-site. Then it took another month to assemble the project on site. We
worked primarily on weekends, as many of the workers were volunteers.
In total, about 200 individuals helped assemble the project. The
installation was in place for one month. It then took about five days to
remove everything from the site…

– The rest of the interview with the artist, at ignant>>
– Luminous Grid, Behance>>
– Environmental Art / Stuart Williams, Photos, Facebook>>