Hit the beach
All beaches in Oahu are free and open to the public, so grab a towel, some SPF, an inner tube or a surfboard, and head to the coastline for some cash-free, unadulterated fun.
View the Nuuanu petroglyphs
Tucked along Nuuanu Stream near Nuuanu Memorial Park and past Alapena Falls, the quick hike will lead you a small cave with animal and human figures carved onto the walls. Added bonus: you can enjoy a pretty waterfall along the way. Jump in... if you don’t fear leptospirosis or whatever.