Three decades after Donald Trump bought New York’s Plaza Hotel and put first wife Ivana in charge of renovations for “one dollar a year plus all the dresses she can buy,” his new castle-like hotel opens this week in Washington. It’s a showcase, and a test, for 34-year-old daughter Ivanka.

Housed in the 1899 Romanesque Revival-style Old Post Office on Pennsylvania Avenue, five blocks from the White House, the $200 million Trump International Hotel Washington D.C. features the first Ivanka Suite ($1,050 a night) and the first spa where her brand, not just the Trump name, is featured. Ivanka helped negotiate the $3 million-a-year lease of the government-owned building and oversaw its redevelopment and design.

“We positioned this building to be the finest hotel in Washington, and it has the potential to be the finest in the country in terms of the amenities we built,’’ Ivanka Trump said in an interview last week, mentioning “incredibly spacious’’ presidential suites, a nine-story glass atrium and guest rooms with 16-foot ceilings. “It’s so majestic, on Pennsylvania Avenue, and it doesn’t take a lot of imagination to realize the potential.’’

With luxury-hotel supply in Washington on the rise -- the hotel at the Watergate, known for the break-in that brought down the Nixon administration, reopened this year after a renovation and a new InterContinental hotel is slated to debut next year -- Trump’s entry faces stiff competition. Room rates, which begin at $625 a night, are well above the $313-a-night average this year through July for luxury hotels in downtown Washington, according to lodging-data provider STR.

“It will be well-received, if not politically, from a product standpoint, and I think it’s going to cause a couple hotels in the city to have to up their game,’’ said Tom Baker, a Tysons Corner, Virginia-based corporate managing director in hospitality at commercial brokerage Savills Studley.

Biggest Ballroom

The new Trump hotel, with 263 rooms and suites and a ballroom that Trump says is the biggest in the nation’s capital, is the result of a two-year renovation, funded mainly by a $170 million construction loan from Deutsche Bank AG that was guaranteed by the Republican presidential candidate. The hotel will have a soft opening Sept. 12, followed by an official one in late October, before the Nov. 8 election.

Win or lose that contest, Trump is poised to cash in on the inauguration in January, when celebrities, party loyalists, foreign dignitaries and business executives will descend on Washington. Hotels typically boost their rates, which can run into thousands or even hundreds of thousands of dollars with minimum stays and nonrefundable prepayment. Rates for inauguration week at the Trump hotel will begin at $1,250 a night. There’s a $500,000 package that includes first-class round-trip air tickets, custom Brioni suits, dinner for as many as 24 guests, spa treatments and Trump family commemorative plates.

“We will be sold out for inauguration,’’ said Mickael Damelincourt, the hotel’s managing director, who previously ran the hotel in the Trump International Hotel and Tower in Toronto, whose developer has been trying to cancel its licensing contract. That project, which Trump has called “a tremendous success,’’ is managed but not owned by the billionaire’s company.

The Washington hotel is controlled by Trump and his family. Donald Trump owns 76.725 percent of an entity called Trump Old Post Office LLC, which leased the property from the government, and Ivanka, Donald Jr. and Eric each own 7.425 percent, a financial disclosure document shows. Trump contributed more than $42 million to the project, according to David Orowitz, a senior vice president at the Trump Organization.