Cienfuegos is a small port city on the southern coast of Cuba that nearly became the centre of another Cuban Missile Crisis in the summer of 1970 when U.S. reconnaissance planes detected the construction of a Soviet submarine base and a communications facility. The story goes that an enterprising CIA analyst closely examined the construction activity around Cienfuegos and noticed that it involved building a number of soccer fields, prompting Henry Kissinger to demand to see President Nixon right away because "these soccer fields could mean war". Why? Because according to the mistaken belief of everyone involved, Cubans were only interested in playing baseball and soccer fields must be meant for the use of Soviet military personnel.
The Cuban Missile Crisis had come about because the Soviet Union had wanted to assert its parity with the U.S. by deploying missiles to Cuba, just as the U.S. had missiles deployed close to Soviet territory all over Europe. The U.S. didn't see things the same way, and asserted that the Monroe doctrine and general U.S. superiority in nuclear weapons meant that the Soviet Union had no right to put missiles on Cuba. Eventually, the U.S. prevailed, although only in part because it secretly agreed to withdraw certain types of weapons from Italy and Turkey if the Soviets backed down in Cuba. The result was a tacit agreement that the Soviets wouldn't deploy nuclear weapons to Cuba so long as the U.S. agreed not to invade the island and topple its Communist regime.
Eight years later, things were a little different. The Soviet Union had now attained broadly comparable nuclear forces to the U.S., meaning that it felt entitled to also assert the prerogatives of a superpower. In an era when superpower relations were in flux and the Soviets were flexing their muscles - they'd also just deployed their first combat troops to the Middle East - they wanted to test the limit of the 1962 understanding. They seem to have impishly wondered if, though banned by the agreement from stationing nuclear weapons on Cuba, they might get away with stationing them on submarines just offshore. Hence the construction of the base.
What had made the Cuban Missile Crisis so terrifying was that at the time there were very limited direct means of communication between the two superpowers; it was only after the crisis that the famous red hotline was created to defuse crises (although it wasn't actually a telephone, much less a red one, but actually a teletype machine - sorry to spoil that). This is why the 1962 crisis is often rightly seen as the height of - and scariest moment in - the Cold War. Communication between the superpowers was much easier in 1970.
Kissinger held talks with the Soviet ambassador and warned him not to test the 1962 understanding; the Soviets quickly backed down. Luckily, the U.S. hadn't had to resort to Nixon's rather ridiculous suggestion of deploying new missiles to Turkey only so that they could then be withdrawn in a measure of manufactured reciprocity. The diplomacy that resolved the crisis was kept secret, meaning the Soviets didn't lose face or have their national pride damaged. In an era of emerging detente, they had no interest in causing World War III over a submarine base in Cuba. The fact a public crisis - much less the threat of World War III - didn't emerge was a sign of how the Cold War had become more regular and predictable. It was a salutary lesson for quiet diplomacy.