A multimillionaire Argentinian family has plunked down $125 million for 1.11 acres at the mouth of the Miami River, a record-setting purchase for a buyer that’s been carefully collecting real estate in Miami’s urban core.

Marking the highest amount ever paid for a piece of undeveloped land in the city’s 117-year history, the sale priced the riverfront parcel Monday at 300 Biscayne Boulevard Way at $2,588 per square foot.

Two CBRE brokers involved in the transaction told the Daily Business Review the buyer could build a 609-foot tower under a 2004 major special use permit or a different tower that conforms to the city’s Miami 21 zoning code

The thin strip of dirt east of the Epic Hotel was created in 1944 as part of a riverbank fill project by the St. Joe Paper Co. The wedge was meant to serve as the staging ground for a second phase of the Epic project, but the waterfront parcel serves as a marina for mega-yachts. The seller is DP Property Holding LLC, managed by Ugo Colombo and Diego Lowenstein.

“The sites at the mouth of the river have really become the premium real estate,” said Gerard Yetming, a CBRE senior vice president. He explained the sale price shows confidence by the buyer, Riverwalk East Development LLC, that an ultraluxury residential tower can be successfully built and marketed on the site.

Robert Given, a CBRE vice chairman who also was involved in the sale, said the price “met our expectations,” but there were higher offers on the property. He explained the seller decided to pull the trigger on the deal because of the speed with which the buyer operated and the belief the new owners would be “good stewards of the site.”

“We had five or six groups that wanted the project all the way to the end,” Given claimed. He said it took less than a month to take the all-cash deal from contract to close.

The people behind Riverwalk, German and Gloria Coto, are part of a family that owns one of Argentina’s largest supermarket chains. Their namesake retail empire evolved from a chain of butcher shops beginning in 1987 and as a discount brand has benefited from the economic malaise that has afflicted Argentina over the past two decades.

The Cotos and other relatives have been involved in purchases within Miami’s Brickell financial district. In May, a company linked to the Cotos bought 18 office condo units at 1200 Brickell Ave. for $6.4 million. Another family-affiliated company paid $9.25 million for a Chevron service station on a 19,466-square-foot lot at 190 SW Eighth St. State filings also suggest the family has its eye on the Colonnade Plaza, an architectural landmark at 1201 Brickell Ave.

The buyers inherited at least one legal issue associated on the riverfront property. The city previously stated a temporary sales center built on the lot in 2007 to support the first phase of the Epic was illegal construction. The city set but has not enforced a January 2012 demolition deadline for the structure.

The seller asked the city Planning Department earlier this year to issue an administrative order allowing the sales center building to remain. That move is opposed by other city officials, who note the building sits on the path of a 22-foot-wide publicly accessible walkway that was promised under previous development plans.