After three brothers, Knights of the First Crusade, discovered the Holy Grail, two of them returned to Europe more than a century later. Richard, died on the route home, and was buried inside a stone coffin in Venice, along with his shield, which served as a marker to describe the way to find the Grail. Several other graves were also located in his burial chamber.
In 1938, using clues researched by his father, archaeologists Indiana Jones and Elsa Schneider found their way from the church-turned-library in Venice through the rat-filled catacombs to the tomb, that had become partially flooded with seeping oil and water. They opened Richard's coffin and discovered the shield. Jones made a rubbing of the inscription on the shield, revealing that the Grail was located near Alexandretta.
However, to protect the Grail from discovery, Kazim and other members of the Brotherhood of the Cruciform Sword attempted to kill the two archaeologists by igniting the oil in the tomb. Hearing the sound of rushing flames and screaming rats, Jones quickly overturned the knight's coffin into the water and used it to trap air in a safe space while the flames surrounded them. Scouting around underwater, Jones found a way out, and led Schneider to their escape route which led them back through to a sewer cover on the piazza outside the library.
Behind the scenes
In the Indiana Jones and the Last Crusade Graphic Adventure the catacombs and the tomb look significantly different from the movie. Indiana Jones explores the catacombs alone and has to pass some puzzles, like to find a combination of medieval icons and to play a musical tune to open some doors.