The historic Plymouth Building in downtown Minneapolis is slated to become a luxury Conrad hotel, according to city documents.

There are only four other such hotels in the United States — even though the uber-luxury brand is part of the $9.7 billion Hilton Worldwide lodging empire.

Conrad Hotels & Resorts offers “personalized experiences with sophisticated, locally inspired surroundings” at 23 properties on five continents, its website says. In the United States, the brand is only in New York, Chicago, Miami and ­Indianapolis, though impending openings range from Fort Lauderdale to Mecca, Saudi Arabia.

“It is definitely positioned above the Hilton name and it would be similar to the Waldorf [Astoria] brand,” said Kirby Payne, president of Rhode Island-based HVS Hotel Management. (Waldorf also is part of the Hilton family.)

The average nightly rate is about $300 at ­Conrad hotels, according to industry sources.

Documents submitted to the city this week indicate that the 12-story Plymouth Building, which sits in the heart of the entertainment district at the corner of 6th Street S. and Hennepin Avenue, will become a 264-room hotel. Officials from the Conrad chain did not respond to phone calls on Thursday.

Minneapolis-based Heartland Realty Investors Inc. is under contract to purchase the hotel, which is now an office building. The firm, which made its name in the multifamily real estate ­sector, has purchased the Hotel Ivy in downtown Minneapolis, as well as the former Holiday Inn Metrodome at Seven Corners, now a Courtyard by Marriott.

Matthew Walter, Heartland’s vice president of acquisitions, declined to comment, saying plans are still in the “preliminary early stages.”

The building, now owned by Historic Plymouth Building LLC, was erected in 1910 and placed on the National Register of Historic Places earlier this year. According to Preservation Design Works, the structure was noted as the “world’s largest all-reinforced concrete office building” — a feat of engineering at the time. Its original Beaux Arts facade was refaced in the mid-1930s in the “starved ­classicism” style that is evident today.

Previous plans by another developer to turn it into apartments apparently fell through.

Now plans call for a bar, restaurant and lobby on the building’s first floor, part of which was once home to the now-shuttered Tom Pham’s Wondrous Azian Kitchen. Documents indicate that Lyon’s Pub will “remain open throughout construction.” Minneapolis-based Ryan Cos., which will serve as the design/builder and developer on the project, declined to comment.

News of the Conrad’s possible arrival is just the latest in a series of announcements involving downtown hotels.

The Radisson on 7th Street S. was recently overhauled into an upscale Radisson Blu, and the Graves 601 Hotel near Target Center was purchased by the Loews Hotels chain.

However, the renovation of the former Nate’s Clothing store into a Warehouse District boutique hotel has hit a snag, according to Tom Biegler, of South Dakota-based Regency Hotel Management.

“It’s probably still going to happen; we had a holdup with the [historic] tax credits, and we’re exploring other options,” he said.