Petschek Palace was a bank that was converted to Gestapo headquarters during the war. Many people of the Czech resistance were tortured there and today the basement remains a museum to their memory. The torture scene of Ata Moravec was filmed in the same basement room where it actually took place.
Subject was also covered in The Assassination (1965) and Operation: Daybreak (1975). In all three cases, the filming took place in Prague, mostly on the authentic locations associated with this real historic event.
It is coincidence that the original floor tiles from the real Moravec apartment have a design that resembles a Nazi swastika. The design was copied by the art department and used on the floor of the Moravec's set - The tiles can be seen clearly in the scene where Mrs. Moravcová is interrogated by the Gestapo.
The interior of the Saint Cyril and Methodius Cathedral was built on stage 8 of Barrandov studios in Prague, Czech Republic. 40 people participated in the construction of the set with dimensions 15 x 35 x 14 sq m. The ceiling weighed 16 tons and was produced separately on the ground and then pulled up with 38 chain winches. 910 bags of concrete, 300 bags of plaster, 90 sq m of glass and 3,300 sq m of wooden boards were used for the construction.
Although it is widely believed that Heydrich was assassinated whilst being driven in the car "SS-3", it is more likely (according to many historical sources) that on the day he was actually being driven in "SS-4". This cannot be confirmed as the Gestapo removed the registration plate before taking photos at the scene.
In the scenes in the crypt beneath the Ss. Cyril and Methodius Cathedral, the presence of a copy of Shakespeare's "Julius Caesar" is a reference to the similarity to the plot of the film as well as the circumstances recounted in the respective works, and a grim foreboding of the fates of the protagonists. The (unknown number, but agreed to be around a dozen) assassins of Caesar, after contriving the dictator's death - under chaotic circumstances not dissimilar to those surrounding Operation Anthropoid - the leaders of the conspiracy, Marcus Junius Brutus and Gaius Cassius Longinus, escaped Rome and raising an army, they were confronted at Philippi in Macedonia. Defeated by the armies of the Second Triumvirate under the leadership of Gaius Octavianus (the future Emperor Augustus) and Mark Antony, they eventually committed suicide to avoid capture and certain execution. Cassius slit his throat after the capture of his camp by Antony, while Brutus ran himself through with a sword with the assistance of a slave, once approached by overwhelming forces. In Shakespeare's play, the battle and suicides constitute the dramatic climax of the play, mirroring the fates of the assassins.
Ober-gruppenführer Reinhard Heydrich in the dystopian series The Man in the High Castle (2015) is portrayed as Oberst-gruppenführer, a higher rank, suggesting a career advancement after his time in Prague.
The trivia items below may give away important plot points.
True to the movie, Karel Curda, betrayed his fellow paratroopers. Curda who had left Prague immediately after the assassination hid out with his mother. Overwhelmed by the thought of being caught he betrayed his fellow soldiers. Curda was present with the enemy at the church during the attack and did identify the paratroopers' bodies for the Nazis. He was given a new identity (Karl Jerhot). He married a German woman and collaborated with the Nazis for the remainder of the war. After Germany fell to the Allies and the war ended, Curda was hunted down and hanged for treason on April 29, 1947.
Josef Gabcík's gun really did fail during the assassination attempt. Josef jumped in front of the vehicle holding a STEN machine gun. As he fired at Heydrich, his machine gun jammed. Resorting to plan B, Jan Kubis pulled a special bomb from his briefcase that had a highly sensitive impact fuse. He pulled the pin and with an underhand motion, he attempted to toss it into the Reich Protector's convertible. Instead, the bomb exploded above the car's running board, just forward of the right rear fender.
According to the book 'The Killing of Reinhard Heydrich' (1989), as the movie portrayed, young Ata Moravec was tortured and after they showed him his mother's head floating in a fish tank Ata revealed the whereabouts of the parachutists when he told the Gestapo that his mother had instructed him to go to the catacombs of the Karel Boromejsky Church if he was ever in trouble.