Sculpture By The Sea has been running in Sydney for about a decade, and runs through October and November on the cliffs between Bronte Beach and Bondi Beach, via Tamarama Beach.
The 2km long seaside art gallery can take anywhere from around 45 minutes to as many hours as you like. You really could spend all day there.
There are some quite steep and narrow paths, so people at extreme ends of the age spectrum could find it difficult, although many of the sculptures are on flat areas. Marks Park in the middle of the walk has the bulk of the artwork, and this can easily be reached without having to climb over anything, except maybe a No Parking sign.
You can find more information at sculpturebythesea.com.