Ritz-Carlton Residences, Boston, South Station Tower/Image courtesy of Pelli Clarke & Partners

As developer Hines begins marketing 166 luxury condominiums, the architect of the 51-story South Station tower surveyed the progress of the firm’s second landmark skyscraper rising along Boston’s Rose Kennedy Greenway.

The South Station project’s decades-long path is nearing the finish line in 2025, placing a glass-wrapped exclamation point atop New England’s busiest train station.

New Haven, Connecticut-based Pelli Clarke & Partners’ has been involved in the project for the majority of the firm’s 47-year existence. Along the way, the project team navigated changes in investors, seven different faces in the Massachusetts governor’s office, the growing popularity of transit-oriented projects and the upheaval to living and work arrangements during a pandemic.

“How could you possibly work on something for two and a half decades, and still have it remain fresh and optimistic? It’s the perfect environment, because you have a front row to seeing society evolve around your project,” Clarke said.

Pelli Clarke & Partners has designed skyscrapers ranging from the Salesforce towers in Chicago and San Francisco to Boston’s One Congress.

In a walking tour of the construction taking place over the commuter rail platforms, Clarke showed off the concrete deck of the future 11th-floor amenity level. Located 137 feet above Atlantic Avenue, the nearly 1-acre vertical park will double as a getaway for office tenants and condo residents with lawns and gardens, water and fire features and a restaurant.

Nearly three dozen 5-foot-deep soil pits are scattered throughout the park, and will support broad-leafed trees providing shade while removing carbon dioxide. Trees will ring a central ellipse gathering spot, and outdoor work stations will be set up for office tenants.

The Boston park will resemble a miniature version of Pelli Clarke & Partners’ vertical park spanning four blocks above the Salesforce Transit Center in San Francisco.

“If you take a look at the Salesforce Park in San Francisco, it looks like a jungle,” Clarke said.

The project vision began during the waning days of the Dukakis administration as a way to refresh the aging train station and bus terminal, leveraging private investment in an air rights project to help pay for transportation improvements. It nearly doubles the capacity of the MBTA bus terminal and improves its connections to the original 1899 headhouse and the MBTA Red and Silver Lines.

Boston and Massachusetts Department of Transportation officials originally offered the air rights development opportunity to developers in 1989, and selected a partnership of Hines and Tufts University Development Corp. in 1991.

Tufts later exited the project, and Hines ultimately partnered with equity investors Dune and APG Asset Management and received $870 million in construction financing from London-based Children’s Investment Fund.

The Collaborative Cos., the exclusive broker, this week launched a marketing list in anticipation of the sales process beginning this fall for the Ritz-Carlton branded Residences. Cushman & Wakefield is marketing the 768,000-square-foot office portion.