For decades, the inside of Brooklyn’s famed Watchtower building was mostly hidden from public view — a private space that was the Jehovah's Witnesses' global headquarters. Now, three years after the Witnesses sold it for $340M to a group of developers, its full reimagining as an office complex is almost complete.

A wholesale renovation — which involved better connecting the buildings, creating publicly accessible outdoor spaces and widespread mechanical upgrades — has turned the structures into a five-building complex now called Panorama.

When it opens, it will feature 635K SF of office space, 35K SF of retail, 15K of hospitality and 55K of outdoor space. The target market is the “creative class,” according to architect Gensler, but the landlords have yet to announce a signed lease.

The revamp — with a reported price tag of $80M — is due to be complete in the fall.

“It was really inward facing and introverted. It was more of a barrier to the waterfront than a connector,” Gensler principal Robert Fuller said during a media tour of the new space Tuesday.

Fuller said his team aimed to “celebrate the quirkiness” of the buildings and their storied history.

“We knew the buildings had great bones," he said. "It was about peeling away the layers that had been added to it."

The site was home to Squibb Pharmaceutical from the 1920s until 1969, before the Witnesses took over the property and used it for over 40 years. The religious group has been selling its extensive Brooklyn holdings over the past decade, as part of its relocation to upstate New York. CIM Group, LIVWRK Holdings and Kushner Cos. picked up the property in 2016, but Kushner sold its stake in the project last year.

The developers and Gensler have pulled all five buildings together as one major campus spanning about 750K SF, or what Gensler principal Amanda Carroll called “an office building on its side."

At 30 Columbia Heights, there is 300K SF of office space and 30K SF for retail on offer. At 25 Columbia Heights, there is 275K SF for office, 2K SF for retail, as well as newly created outdoor space — dubbed the jewel-box, it could also be an event space — and a chance to brand a company to the passing Brooklyn Bridge traffic.

The three buildings at 50 Columbia Heights, 58 Columbia Heights and 55 Furman St., which were built sometime in the 1870s, could serve as offices, restaurants, retail or potentially a hotel.

Gensler’s designers said the entire project could serve one major tenant, but it has been designed with a multi-tenant approach in mind. The asking rents have not been made public and leasing is being handled internally.

“It’s an incredible opportunity for Brooklyn,”  Downtown Brooklyn Partnership President Regina Myer said. “Just like Empire Stores, it has the opportunity to bring world-class tenants.”

There is no doubt Panorama will face some competition. There is nearly 7M SF of newly constructed office space due to deliver by 2022, and more is on the way. Savanna filed plans back in May for a 23-story office tower at 141 Willoughby St. In Greenpoint Rubenstein Partners and the Acme Smoked Fish Corp. are turning 30-56 Gem St. into a 583K SF office building.

Meanwhile 25 Kent Ave., the first ground-up, spec office development in Williamsburg in decades, still has yet to publicly announce a tenant for the 500K SF building, despite claiming to be close on an anchor tenant deal in November.

Many have lamented the fact that the borough has yet to land a market-moving tenant, although this year has started to change that tune. Rent The Runway took 83K SF at 10 Jay St., marking the biggest relocation from Manhattan in two years.

Coworking companies are becoming more active in Brooklyn, too, according to Colliers, with The Wing taking 18K SF at 71 North Seventh St. and Soho Works leasing up 48K SF at 10 Jay St. Meanwhile, the city government renewed its 342K SF lease at 250 Livingston St. in what was one of the biggest leases of the year.

In a statement, a spokesperson for LIVWRK and CIM Group said the owners are having discussions with “wide range of creative office tenants [who] appreciate the large floor plates, location and historic nature” of the Panorama.

“They are looking for a large company to relocate from Manhattan … 25 Kent tried that, and so far we haven’t heard,” said TerraCRG Managing Director Caroline Pardo, who said she has toured the Panorama building but has not taken clients there. "Domino tried that — and again they haven’t had any movement. I think it’s really that size that hasn’t had any traction."

But Pardo said the city's Relocation and Employment Assistance Program is a major draw, and noted that the under-10K SF segment is the most active part of the leasing market.

“They will find their tenant, it’s just a matter of time,” she said.

Dan Marks, also of TerraCRG, said Brooklyn is ready for a big, well-known company, and Panorama could be the location to bag it.

“I don’t think you will get any more high-profile location, with visibility and signage,” he said. “This is as good an opportunity as Brooklyn has to present itself to these large tenants ... Hopefully the timing is right.”

CORRECTION, AUG. 21, 6 P.M. ET: An earlier version of this story did not use Amanda Carroll’s full name. This story has been updated.