Turin and Innsbruck will join Madrid as co-hosts of this year's Davis Cup Finals from 25 November.
Last year's finals were postponed because of the coronavirus pandemic, and the same 18 nations will contest this year's event.
The International Tennis Federation says the finals will be played over 11 days rather than seven.
Great Britain will play their Group C games against France and the Czech Republic in Innsbruck in Austria.
Each city will host two of the six groups - Spanish capital Madrid will host Group A, featuring Spain, Russia and Ecuador, and Group B, containing 2019 runners-up Canada, Kazakhstan and Sweden.