Evening view of The Old Post Office Pavilion (L) showing the corner of Pennsylvania Ave NW and 12th St NW, Washington, D.C. (Photo by Tracy A. Woodward/The Washington Post) (Tracy A. Woodward/THE WASHINGTON POST)

Donald and Ivanka Trump will be in town Tuesday to unveil the latest on their plans to turn the Old Post Office into a luxury hotel.

Their company, the Trump Organization, finalized a 60-year lease with the federal government for the property in early August and local officials including D.C. Mayor Vincent C. Gray (D) and Del. Eleanor Holmes Norton (D-D.C.) are expected to attend.

Donald and Ivanka called briefly on Monday to provide an update on the project. Here are some important takeaways so far:

The vast majority of the building will be preserved.

The Old Post Office is listed on the National Register of Historic Places and the Trumps’ plans have already gone through an extensive review by agencies that protect federal buildings, including the Commission on Fine Arts and the National Capital Planning Commission. Because the exterior is protected, the Trumps proposed changing very little of it.

“The building itself is magnificent and the great asset that we have, and obviously its location on Pennsylvania Avenue, so everything we are doing is to build on that rather than detract from it,” Ivanka Trump said of the building.

Instead, the Trumps are mainly determining how to preserve and accentuate some of the exterior’s features, like windows and trim. Ultimately, they will be adding new signage in and around the building advertising it as “Trump International Hotel, Washington, D.C.” They will also be re-instating some original features of the building, such as a vehicular entrance along 11th Street and ground level access from Pennsylvania Avenue through the center of the main level.

Certain aspects of the building will pose challenges as it is converted into a hotel, particularly the very wide corridors it has upstairs. That isn’t usually a great use of space in a hotel but Donald Trump said they have adapted. “I think one of hardest things was — you know the hallways upstairs, they’re tremendously wide...It’s very expensive to have hallways at that size,” he said. Once it opens he thinks the hallways will “add to the feeling of luxury.”

●The rooms will be some of the largest and likely most expensive in town.

In part because of the building’s configuration, the Trumps will be building hotel rooms averaging about 600 square feet, which Ivanka Trump said will be the “the largest in all of D.C.” There are expected to be 271 of them in all, though Ivanka Trump said another one or two might be added down the road. Room rates have not been set, the Trumps said, but they expect the hotel to be the best in Washington and for the project to be profitable. Hotel analysts say the Trumps will probably have to get $700 or more per stay, depending on occupancy rates.

Access to the clock tower will remain open to the public.

The Trumps will not own the building (they are leasing it) and they won’t even be operating the historic clock tower, which offers some of the greatest views in Washington. That remains under the purview of the National Park Service and access to the tower will remain open to the public.

Having fanny pack-toting tourists walking in a luxury Trump property might seem odd but it happens all the time at the 58-story Trump Tower, the Fifth Avenue building where Donald Trump lives, works and films “The Apprentice.”

The rear annex will be replaced by an enormous ballroom.

Some may recall a failed effort in the 1980s to rehab the Old Post Office, an effort still evidenced by a vacant and crumbling glass-encased rear annex. The Trumps plan to keep just the steel from that structure and replace the glass with backlit marble, inside of which they will build a 50,000-square-foot ballroom, one of the biggest in Washington, likely to be called the “Presidential Ballroom.”

“We wanted to create something that was distinctly new and modern,” Ivanka Trump said.

The Trumps say they are lining up “super-luxury” retail and restaurants.

The hotel will have two restaurants, one out front facing Pennsylvania Avenue and another inside. A third space, also facing Pennsylvania Avenue, will likely be for a fashion retailer. Bethesda-based Streetsense is managing the retail space, but the Trumps have a relationship with Tiffany & Co. as well as New York chefs such as Jean Georges.

The Trumps will try to connect the hotel to their golf resort in Loudoun County, Trump National Golf Club.

It will probably open by the end of 2015 or early 2016. Ivanka Trump said she’d love to have a grand opening at the end of 2015 — which could provide some good holiday season business — but there are still agencies moving out of the building and the Trumps aren’t certain they will have it in their hands by this spring.

●The Trumps are putting a lot of money into the project.

Donald Trump has been criticized in the past for leasing his name to other developers for projects that didn’t pan out, but that isn’t the case here. The Trumps and the Trump Organization will own the project completely, meaning they are putting up whatever money is likely needed for the $200 million project other than money borrowed to build it, as happens with almost any commercial project.

Follow Jonathan O’Connell on Twitter: @oconnellpostbiz