FRANKFURT — It has been derided as a hot tub party for world leaders and praised as an emblem of post-Cold War collegiality. Nearly 35 years after it was born in a chateau outside Paris, it still has no public phone number, website or e-mail address.

Yet the Group of 7 summit meeting has endured, and while almost as famous for its gaffes as for its achievements, it is still the only forum where leaders of the world’s wealthiest nations meet each other once a year to grapple with the most intractable geopolitical issues.

Now the G-7 seems almost to have come full circle, from its origins in the wake of the Vietnam War to a new era of retrenchment and tension with Russia.

Russia’s annexation of the Crimean Peninsula prompted the other seven members to refuse to come to Sochi, where Vladimir V. Putin had prepared ostentatious lodgings for the visiting leaders. Instead they will go to Brussels, the somewhat dour capital of the European Union. The forum, which has also been known as the G-6 or the G-8, depending on the size of the guest list, is once again a group of seven. The hot tub has grown frigid.