In those days it was unusual for a top GM to play in Open Swiss tournaments, but Larsen entered, and won, many of them.
After Larsen won the Monte Carlo 1968 tournament ahead of Botvinnik, Smyslov, Hort, Robert Byrne, Portisch, and Pal Benko, he had racked up an incredible string of five consecutive first place finished in major tournaments.
This game, which made the cut in the book The World's Greatest Chess Games as one of the one hundred best games of all time, was played in the semifinal candidates match, Bled, 1965 and features an intense tactical battle.
The match was tied at two wins apiece with five draws and the winner would face Boris Spassky in the final candidates match to determine the challenger for World Champion Tigran Petrosian.
In the book, the game was rated by Graham Burgess as a 10 out of 15; the lowest score making the cut was 9. The games were rated on quality and brilliance of play by both players, instructional value and historical significance. It's amazing neither of their heads explode while calculating the variations in this game!!
The game is a good one to actually set up a board and play through so you can practice your powers of visualization. I have made a link to a pdf file in Dropbox you can download and printout HERE.