Alekhine, Euwe, Bogoljubov, Flohr, and Sultan Khan, all played in the world elite tournament at Bern in 1932, including the Swiss Hans & Paul Johner, Grob, or Naegeli (who beat reigning World Chess Champion Alekhine in a separate Quadrangular Easter event at Bern the same year). 

Much later, the veteran players Geller, Unzicker, Szabo, young Kamsky, Klinger, King, and Korchnoi, dominating a training match for the Olympiad, played in the capital of Switzerland.

Pia Cramling made her final norm to become a *male* GM during an Open Festival at Bern in 1992.

Alexander Alekhine won the world-class tournament from Bern in 1932. Recolored photo, date unknown: George Grantham Bain Collection (Library of Congress) / Wikipedia

World Elite tournament 1932 

Later:

Max Blau Memorial (I. Invitation tournament) 1987

II. Invitation tournament 1988 

III. Invitation tournament 1989

FIDE Zonal 1990

Training team match with Korchnoi 1992

Volksbank Open series

and Open Predecessors

Three international invitation tournaments had been held in Bern from 1987 to 1989 (Campora and Geller won in 1987, Cebalo in 1988, M. Gurevich in 1989), followed by a FIDE Zonal in 1990 (Gad Rechlis from Israel won, he and Eric Lobron from Germany as sole runner-up qualified for the next stage); as well as two longlasting series of Open Chess Festivals in the 1960/70s, and again from 1987 on up into the 21st century. 

Euwe played a huge number of matches against historical figures; Reti, Maroczy, Colle (twice), Capablanca, Alekhine (three times), Bogoljubow (three times), Spielmann, Flohr, Keres, Grob, Pirc, Donner (twice), Fischer (an informal Mini-Match in the USA in 1957, two games, +1=1 against 14-year-old future world champion) and in his late years, Sosonko.