A 30,000-square-foot rooftop park that might even include an ice skating rink.

A dramatically enlarged Skydeck Chicago — possibly spanning two floors — with an “enhanced thrill experience” to give 1.7 million annual visitors “a new perspective of what it’s like to be 1,353 feet in the air looking straight down.”

A first-of-its kind, 50,00-square-foot “digitally interactive and immersive family entertainment experience” in that enlarged Skydeck operated by “one of the largest media and entertainment companies in the world.

One day after disclosing plans to spend $500 million to remake Willis Tower “from street to sky” by 2019, tower owners Blackstone and Equity Office on Wednesday fleshed out their vision for creating a “retail and entertainment destination that is missing in the West Loop and will be unmatched by any other destination in Chicago.”

“The execution of our vision for Willis Tower will add 300,000 square feet of retail, dining and entertainment options on six levels at the base of the building brought together in a spectacular winter garden and encapsulated under a magnificent curved glass skylight that will provide a vertical perspective of the tower that reaches all the way up to the sky,” said Paul Kurzawa, managing director of development for Equity Office.

Kurzawa said interest from retailers has been so strong, more than half of the 300,000 square feet of new restaurant and entertainment space is “already in lease negotiations.”

“We’re also building a 30,000 square foot rooftop park that will provide a new meeting place for workers and visitors alike. This place will be there for relaxation, music, and perhaps even a little ice skating,” he said.

As for the Skydeck, the makeover will capitalize even more on the “unbelievable views, the thrill of elevation and build on the success of the Sky-ledge attraction that allows 1.7 million annual visitors to stand on a translucent ledge and look down.

“We’re designing a new observation experience that will increase in size and feature a number of new attractions. We will introduce an enhanced thrill experience that will give visitors a brand new perspective of what it’s like to be 1,353 feet in the air looking straight down,” Kurzawa said.

“We’re in the final stage of negotiations with one of the largest media and entertainment companies in the world to open a first-of-its-kind, 50,000 square foot, digitally inter-active and immersive family entertainment experience. We look forward to sharing more information about this exciting addition with you very, very shortly.”

Architects noted that the building once known as Sears Tower was built with the idea of separating the “urban streetscape” from the building to “minimize” pedestrian traffic along the sidewalk.

The new design will “break this barrier” and “re-energize” the downtown area, architects said. The plan also includes 150,000 square feet of space for “exclusive tenant use,” including a “full-service fitness center, expansive tenant lounges, private event space and concierge services.”

The plan is billed as the “first major renovation” in the building’s 43-year history.

Jon Gray, global head of real estate for Blackstone, noted that the $500 million investment that will create 2,500 jobs represents the “largest single capital investment in a property” in the company’s history.

He offered two reasons for the extraordinary investment — without a penny of taxpayer money: The “downtown renaissance” that has attracted a parade of corporate headquarters relocations, led by McDonald’s and the fact that Blackstone and Equity Office are “big believers” in the iconic Willis Tower.

“The scale, the architecture, the views, the location, the access to transportation. There is enormous potential to create something very special,” Gray said.

“Willis Tower has been under-managed and under-invested in for a number of years. And that changes today.”