joe risoto jr. takes us to the santa cruz mountains. >> reporter: in the santa cruz mountains, is a park filled with giants. big basin, redwood state park, challenge's first state park. and, like the name says, filled with giant redwoods. >> what makes it so special and the reason people were so inspired to protect it over a hundred years ago is these amazing redwoods. >> reporter: more than 120 years ago. a fund helped establish this big basin as a state park. >> it really spurred the creation of the state park system here in california. >> reporter: these days, when she visits this park's to sound the alarm. >> so this is one of the old-growth trees that unfortunately did not survive the fire. >> reporter: in 2020, bolts of lightning set off the massive czu lightning collection fire. more than 90% of big basin burned. >> this chimney is just an indicator of what was once here, which was this gorgeous historical building. >> reporter: along with all of its historic park buildings, what burned here