When President Obama shuttered Russian compounds in Maryland and New York as retaliation for alleged Russian interference in the U.S. presidential election, Russia’s ambassador to the U.N. accused him of "going after our kids."

"They know very well," said Vitaly Churkin, "that those two facilities are vacation facilities for our kids."

While it’s true that the Russian diplomatic corps has long used the leafy estates on the Eastern Shore and Long Island as retreats, with officials and their families swimming, fishing and playing tennis, U.S. intelligence says that the mansions doubled as surveillance outposts for Russian spies.

Closing them, said an intelligence official, "is certainly more symbolic now than operational," since the way signals intelligence is gathered over the past several decades has changed. But officials still think they are used for more than just recreation.

U.S. officials say that as far back as the Reagan administration, the intelligence community believed that the Soviet Union was using both compounds to steal communications from the U.S. government and defense contractors.

Related: U.S. Unveils Plan to Punish Russia for Election Hack

Both are extravagant former mansions obtained early in the Cold War and maintained by first the Soviet and then the Russian foreign ministries. They are artifacts of a time, say officials, when the U.S. and the Soviet Union played a great game of electronic spy vs. spy, often siting recreational facilities for diplomats near communications nodes.

Equipment is removed from the Russian compound at Pioneer Point in Maryland. NBC News

The waterfront estate at Pioneer Point in Centreville, Maryland, was viewed as the more significant of the two shuttered Russian compounds, largely because of its location near the Baltimore Washington corridor.

The Centreville compound consists of a three-story mansion and ten Russian-style "dachas" on the Chester River on Maryland’s Eastern Shore. The mansion is a monument to American capitalism — it was built by Jacob Raskob, a financial advisor to the duPont family and the builder of the Empire State Building.

Raskob chose the location because of its spectacular views. Those same views, from an electronic viewpoint, were ideal for the Russians, according to U.S. intelligence officials and a high-ranking Soviet defector who told his tale to the FBI and NSA. Arkady Shevchenko, who was the undersecretary general of the United Nations at the time of his defection in 1978, had spent time at all the Soviet diplomatic facilities.

Shevchenko described his Soviet colleagues as "very happy" when they were able to acquire the Pioneer Point property in the mid-1970s.

The most thorough description of the facility’s value to the then Soviet and now Russian intelligence services came in a series of monographs on Soviet intelligence published by the Australian National University’s Strategic and Defense Studies Centre in the late 1980’s.

Desmond Ball, the centre’s late director, wrote of Pioneer Point, "the complex is extremely well-placed for SIGINT (signals intelligence) operations."

He explained that the location was in the main microwave communications corridor between Washington and the massive U.S. Naval base — the world’s biggest — in Norfolk, Virginia. Ball also noted that "NSA headquarters at Fort Meade is 35 miles directly west; the large Navy communications station at Annapolis (used to communicate with nuclear submarines) is 20 miles west southwest; and the NSA’s Propagation and Research Laboratory on Kent Island is 15 miles to the southwest."

Officials say the Soviets and their Russian successors were brazen about the facility’s mission. Starting in the late 1970s, antennas went up on the main building. Soon, the mansion and surrounding property was festooned with all manner of antenna for capturing communications and other signals.

The Reagan administration began a major communications effort to secure the links and also cut down on the Soviets’ access to U.S. communications technologies, thwarting plans to install a large satellite dish at Pioneer Point. Soviet diplomats said the dish was for reception of Soviet TV shows. The U.S. believed it was a way for the Soviets to downlink U.S. military communications.

The Raskob Estate at Pioneer Point on Maryland's Eastern Shore, shown here in a 1940 aerial photo, was purchased by the the Soviet Union in the 1970s. The Obama administration is shutting access to a New York retreat and the Maryland waterfront compound where Russian diplomats played tennis, sailed and escaped the political bustle, saying those doubled for intelligence activities. The Baltimore Sun via AP

After 2000, during the Bush administration, there were concerns within the intelligence community about how close Pioneer Point is to St. Michael’s Maryland, where Vice President Richard Cheney and Defense Secretary Donald Rumsfeld had second homes. The homes were less than 20 miles south of Pioneer Point.

May Day Parties and Summer Camp

Less is known about the Upper Brookville, New York, property. In the past, U.S. intelligence saw it as an outpost of the Soviets larger recreational complex at Glen Cove, which rivaled Pioneer Point in its access to U.S. communications. The two New York properties are only five miles apart on Long Island’s North Shore.

The Upper Brookville location, like both Pioneer Point and Glen Cove, was a mansion in a choice location when the Soviets purchased it in 1954. Adjacent to the Mill River Country Club, with 14 acres of secluded property, it too had great access to communications links and was close to several defense contracts facilities farther east on the island. The Russians added a second large building to the property, and real estate records put the value of the whole compound at close to $10 million. It is hidden by woods, and approached by a winding driveway off of Mill River Road.

A former neighbor told NBC News that the Russians used to have big May Day parties at the estate during the Communist era, but that it was otherwise very quiet.

More recently, said a current neighbor, the site seems to have been used by the Russians as a summer camp. During the summer, she said, "school buses would go in and out filled with children." Otherwise, there was little activity visible to the neighbors.

resident Barack Obama on Thursday ordered the expulsion of 35 Russian suspected spies and imposed sanctions on two suspected hackers and three companies that allegedly provided support to cyber operations by the country's GRU intelligence service as well as the closure of two Russian compounds, including this estate at Pioneer Point in Maryland. NBC News

Once she said, her dog got lost, and a voice with a Russian accent called her to come pick it up. The dog was outside the gate when she arrived, so she never saw inside the compound.

Shevchenko, in his discussions with the U.S. government and the media, lumped Upper Brookville, Glen Cove and Russia’s diplomatic missions in Manhattan together, telling one interviewer that combined, the New York properties gave the Soviets their most sophisticated equipment anywhere for electronic surveillance.

The great value of Upper Brookville and Glen Cove was the Long Island Sound, just a few miles to the north of both. The geographic contours of the sound provided "excellent microwave propagation characteristics," wrote Ball, "commonly known as Microwave Alley.’" He added that the FBI found that signals from as far as 100 miles away could be intercepted at either location.

Moreover, the facilities had clear electronic views of several critical U.S. facilities across the Sound in Connecticut, including the U.S. Navy’s submarine base in Groton, Connecticut, and the Naval Underwater Systems Center in nearby New London.

The Russian compound in Upper Brookville on New York's Long Island. NBC News

Ball added that Upper Brookville "presumably coordinates SIGINT activities" with those at Glen Cove.

Since the Cold War, of course, things have changed. The U.S. has secured its vital communications — and communications technology has changed. Microwave is not as significant a carrier as it was in the 1970s and 1980s. Fiber optics lines have replaced much of it. Cell towers are now more important than microwave towers.

A senior U.S. intelligence official told NBC News that the New York and Maryland facilities are under constant U.S. surveillance. They are not believed to have played any role in the election hack, said the official, and in 2016 have no intelligence gathering capabilities that the Russians don’t have at other facilities.

Jeffrey Richelson, the intelligence historian, agreed that the facilities were legacies of the Cold War, but wasn't so sure they were artifacts. "Whether they're artifacts," he said, "depends on the current use."

According to the State Department, both the Centreville and Upper Brookville facilities were to be vacated by noon Friday. The Glen Cove, Long Island property, despite earlier media reports, was not affected by the president's executive order.