The O’Connell Library Pocket Park, seen under construction in June, opens Friday with butterfly lights and eight new trees. (Photo: Mark Jaquith)

Two parks open for public use at events this weekend in Cambridge: The O’Connell Library Pocket Park at a 3 to 4:30 p.m. Friday event and the Glacken Field and Playground from 11 a.m. to 1 p.m. Saturday.

The library pocket park at 48 Sixth St., East Cambridge, includes distinctive butterfly lights – internally illuminated cubes of orange and black, reminiscent of butterfly wings – and eight new trees, and has come together over the past 19 years of work by residents.

As the East Cambridge Open Space Trust – founded and funded as result of a legal settlement with the original developer of what is now known as The Canal District in Kendall Square – residents maximized funds by putting the park on city-owned land, to overcome high land prices, said Mark Jaquith, a former trustee. In addition, the park is “in a high-density setting relatively far from existing parks.”

“The trustees themselves thought of the library site” and got design help from a nonprofit, eventually hiring landscape architects and designers, Jaquith said.

While the design was well received by the Library Department, city councillors and staff from Finance, Public Works and Community Development, “it took years more of persistence by the trustees to achieve any real progress – even with a substantial financial contribution by us,” Jaquith said.

The Friday opening includes an hourlong speaking program and, in the final half-hour, an outdoor storytime. Refreshments will be provided.

Glacken Field and Playground at 600 Huron Ave., in Strawberry Hill south of Fresh Pond, now includes two Little League fields with dugouts, backstops and a bullpen and batting cage. The tot lot area has been reconstructed with new play structures, rubber surfaces, a wave curb and a spray pad. The entire park has been surrounded by a pathway with new landscaping and play features, and it connects with the nearby Fresh Pond Reservation. The work began with a community process and design in the fall of 2019, with construction starting May 25.

The opening event includes free entertainment and refreshments.