The fourth Design Biennial Boston, a program celebrating emerging architects, landscape architects and designers, launched this week. Since March, four firms selected from the Boston area — Cristina Parreño Architecture, GLD, Landing Studio and MASS Design Group — have been preparing the site-specific installations that are on view at the Rose Kennedy Greenway through September 25th.

“Boston has a vibrant talent pool of designers, and these four installations remind us of how creative artists can be when given opportunities,” said Mayor Marty Walsh. “Boston is on its way to becoming a municipal arts leader, and implementing this type of exciting and thoughtful work into the public realm is what gets us closer to that goal.” Earlier this year, Walsh called on citizens to tweet their ideas for a City Hall plaza makeover.

Here’s a peek at the Biennial designs.

(Credit: Design Biennial Boston)

“Marginal” was created with eight recycled oak pilings from a Boston Harbor shipyard.

From Landing Studio: “‘Marginal’ measures change in the site’s natural slope toward the harbor and brings subtle awareness to our movement across it.”

(Credit: Design Biennial Boston)

“Tectonics of Transparency: The Tower” is a 17-foot-tall landmark made out of 350 glass blocks.

From Cristina Parreño Architecture: “Working as a periscope, it recuperates the views from the elevated highway that only two decades ago rumbled overhead. From the more distant past, it recalls a lighthouse guarding the harbor before the city extended its landform into the water.”

(Credit: Design Biennial Boston)

“Grove” is made of resin-infused fiberglass.

From GLD: “By peeking inside, visitors not only see the voids that were formed around inflated molds, but might also catch glimpses of others doing the same. Such chance encounters are common to urban life, but here they are exaggerated, reframed, and celebrated as a moment of both estrangement and connection.”

(Credit: Design Biennial Boston)

“Lo-Fab” is a lattice-like structure made from custom metal joints connected to machined lumber pieces. It covers two curved paths that lead to a contained, personalized space open to the sky and screened from the city.

From Mass Design Group: “The formation of an intimate space for only a few occupants at any one time identifies this spot on the Greenway as a contemplative retreat in the midst of the whirling activity of people and vehicles.”