As the world marks 25th anniversary of the fall of the Berlin Wall, Robert McCarthy and Marc Fisher, two former Post Central European correspondents, look back at history as it unfolded in front of their eyes. (Davin Coburn and Gillian Brockell/The Washington Post)

In a bleak corner of the German capital, a tour group of teenagers reverently approached a defunct power plant covered with graffiti and coils of barbed wire. They eyed it, awestruck, as first-timers in London or Paris might Big Ben or the Eiffel Tower.

Their guide stood before the edifice — now transformed into a club widely dubbed the pinnacle of hardcore nightlife — and dramatically introduced it.

“This,” he proclaimed, “is Berghain.”

A temple of urban pleasure drawing thousands each weekend for hedonistic parties lasting days at a time, Berghain is a symbol of Berlin’s latest incarnation. Twenty-five years after the fall of the Berlin Wall — an anniversary marked Sunday — this brooding metropolis has gone from being a Cold War capital to a magnet for untamed youth.

Relatively cheap rents and a fiercely bohemian sensibility have transformed Berlin into what Prague was in the 1990s and Buenos Aires was in the 2000s — a beacon for penniless hipsters, international artists and merrymakers of every stripe. There is a population boom of the young: More than 205,000 people have come here from around the world over the past three years, and the majority of them are under 40.

Tourism is also surging. And, surveys show, many are coming at least partly to party — or, better said, to partake in a spurt of decadence not seen since the cabaret days of the 1930s.

The cathedral of cool is Berghain, a seething world of drugs and sex that boasts hours-long lines and a random door policy that strikes fear into the hearts of all who try to enter. But the city is overflowing with ever more new temples to youthful exuberance, liberation and counterculture. Seedy watering holes that let you pay for your beers in Bitcoin. Urban communes promising life “without bosses” or “nuclear families.” Vintage burlesque shows serving homemade cupcakes. City-subsidized art studios. Computer hacker clubs. DJ conventions. Stores so cool you have no idea what they’re selling.

The city’s sybaritic promise is luring the likes of Tima Dzhergeniya, a 31-year-old Russian émigré who barely remembers the fall of the Berlin Wall. But he vividly recalls his first night at Berghain, during a semester abroad in 2012. It moved him so deeply that he relocated here a year later. Now residing in a two-room apartment for $600 a month, he is supporting himself with a marketing job and living for the weekends, when he and other members of the “Berghain Army” — a group of devotees who dress almost exclusively in black — hit the club.

“I read Christopher Isherwood and saw ‘Cabaret’ before coming to Berlin, and in some ways, I think you can say those days are back,” said Dzhergeniya, who, like many of the newcomers, does not speak fluent German and gets by with English, the lingua franca of Berlin’s partying classes. “I think there’s really one reason people move here: the feeling of absolute freedom.”

Berlin is no stranger to a good time. Decadent and taboo-breaking before the rise of Adolf Hitler, the club scene here inspired Isherwood’s seminal work, “Goodbye to Berlin.” David Bowie and Iggy Pop roosted in West Berlin during the 1970s, and the city’s legendary club SO-36 set a standard for the age of punk.

After the fall of the wall, the electronic music and art scenes percolated throughout the 1990s and 2000s. The center of the city’s cultural gravity shifted east, thriving in the abandoned and run-down buildings of Berlin’s urban core. More recently, Berlin’s nightlife has obtained what observers call a critical mass, becoming bigger and more diverse and flirting with the “Big M”: mainstream.

Indeed, bespoke cocktail bars and fashion shows are gaining a foothold, along with the more moneyed newcomers who are the subject of broad derision for driving up rents. But despite persistent gentrification, the city and its scene remain aggressively non-glitzy. Berlin is, in effect, the anti-Paris — a capital of true grit where, in the hippest neighborhoods, Ferraris and BMWs are still more likely to be keyed than gawked at with envy.

“Berlin is going mainstream in the sense that the scene is now in a new cycle,” said Sven von Thülen, a DJ and co-author of “Der Klang Der Familie: Berlin, Techno and the Fall of the Wall.” “But Berlin still hates glamour. It rejects celebrity culture. That has not changed, and I don’t think it ever will.”

Berlin’s “shabby chic” is going global. “Berlin Fridays” — attempts to capture the raunch and excess of Berghain — have popped up in New York’s revered club scene. In Athens, bars are taking inspiration from Berlin’s secondhand style, importing its makeshift blend of salvaged furniture and distressed walls. Even London’s competitive mayor, Boris Johnson, tipped his hat to Berlin last year, writing in an op-ed that “I look around modern Berlin and I see a culture so generally cool and herbivorous that the bicycle is king.”

There are also indications that the explosion of youth culture is fueling a different kind of economic boom here.

Berlin is one of Germany’s poorest big cities, often portrayed as an island of inefficiency in a country otherwise known for precision and competence. Its new airport, for instance, is years late and more than $2 billion over budget. But in recent years, Berlin has seen an explosion in so-called creative industries — ranging from art spaces to tech start-ups to advertising firms — that have capitalized on its status as a beacon for youth.

Growth in the sector is being fueled by such companies as Wunderlist, a start-up based on an app that allows users to manage a multitude of to-do lists on various devices. Holed up in a new high-tech hub that abuts a surviving fragment of the Berlin Wall, the company has gone from almost nothing in 2010 to having 60 employees and financial backing from U.S.-based Sequoia Capital.

The company’s youthful staff enjoys a relaxed and innovative work environment that makes Googleplex look staid. Wunderlist, for instance, has recently adopted an office model that virtually does away with traditional managers and assigned workloads, instead embracing an egalitarian system of revolving leaders who must sell their ideas to co-workers and convince them to sign on to temporary teams.

“Berlin has a refreshing youth to it, and we are using that to our benefit,” said Christian Reber, Wunderlist’s 28-year-old founder and chief executive, who was born in the former East Germany.

He bristles when outsiders “label” the city and other parts of Germany as the “former east” and “former west.”

“It’s been 25 years,” he said. “I would rather think about the future than the past. It is time to move on.”

Stephanie Kirchner contributed to this report.