One of the Bay Area’s newest waterfront walkways is set to open this fall in Oakland. It is one-tenth of a mile long, and it cost $1.6 million to build.

The new path is part of the San Francisco Bay Trail, which, if completed as expected by 2025, will form a continuous, 500-mile ring around the bay’s shoreline, giving people greater — and free — access to the region’s defining natural feature.

More than half of the trail, 313 miles worth, has already been built. The longest continuous segment is 26 miles, from Alviso in the South Bay to East Palo Alto. But filling in the rest of the trail will not be easy, or cheap.

“The low-hanging fruit has been picked,” said Nancy Wenninger, assistant general manager of the East Bay Regional Park District. “From now on, it’s the hard connections and the expensive ones.”