Herzen Castle is a location in Professor Layton and the Diabolical Box. It was an old castle located at the far north side of Folsense, past the forest, that was the home of the Herzen family. Under the casle was an exposed mine, which had been pumping out halluciogenic gas into Folsense, causing the residents to see the town as it was 50 years before. The true Folsense is revealed upon the collapse of Herzen Castle, when the debris blocks the gas from escaping.
Over 50 years before Diabolical Box, the castle was built by Duke Herzen. The castle was for him and his two sons, Anton and Fredrich, to live in. During this time, many dances and social gathering took place inside as well.
All of the townspeople in Folsense believed that a vampire lived in the run down castle, since everyone who knew the Herzens had evacuated.
Chapter Six: The Road to Herzen Castle
When Layton and Luke arrive at the castle, Parcelle has apparently just escaped being dinner for the vampire. Nigel, the Herzens' butler, won't let Layton and Luke come into the castle unless they have solved 80 puzzles beforehand.
Chapter Seven: An Encounter at the End of the Line
Once done, Nigel lets them inside, where Anton makes his first personal appearance. Then Anton and Layton have a conversation about the Elysian box and its history. Anton knew that it was a Herzen family heirloom, but apparently due to his personal dislike of it, he disposed of it.
Anton invited Layton and Luke to stay the night. As they slept, they were locked in the cellars by Anton. It is here Anton tells them that he is a vampire. Layton and Luke manage to escape from the cellars, but Layton decides that he and Luke must stay and investigate the castle before leaving, thinking that it is the key to solving the mystery. So they go back, looking for Anton. Then, it is here they meet Katia.
Katia implores for them to leave, but before they can, Anton confronts them, annoyed at being disturbed. When he saw Katia, he became bewildered, mistaking her for someone called Sophia. Katia hid behind Layton, which lead Anton to believe that 'Sophia' had left him for Layton, so challenged him to a duel. Being one for fair play, he pointed out to Layton that there were several swords to use, but only one was real.
Choosing the correct sword, Anton and Layton engage in a duel. After a short fight, however, Anton starts hyperventilating and nearly collapses.
The mystery of Anton and his apparent immortality and his ties with the Elysian box were revealed. Layton explained that when the miners were looking for gold in the mines 50 years ago, they accidentally opened a pocket of halluinogenic gas. It caused the townspeople to have terrible visions of what they feared the most, which made them ill. The Folsense everyone could see was actually a hallucination influenced by the old photos put up in the train station.
Katia then explains to Anton that Sophia had evacuated with the townspeople too; not because she was scared or had fallen in love with another man, but because she was pregnant with their child. She had kept it secret from Anton to spare him of more pain. Katia then told Anton that he is her grandfather, and that Sophia had died from old age the year before.
Anton flies into a rage of disbelief over anger and loss for Sophia, and he accidentally destroys a chain holding up the positively gigantic chandelier in the castle foyer. It then crashes down into the floor and destroys the whole castle. Layton, Luke, Katia, and Anton then get outside before the castle is completely destroyed. With the castle debris blocking the vent for the fumes, Folsense is revealed to be a long abandoned and ruined place, and Anton an old man. After that, Anton and Luke open up the Elysian box's secret compartment which contained a message only meant for Sophia, finding that Sophia had actually written back just days before her death
The rickety bridge is found at the southern end of the castle and serves at the only visible entrance into the castle. It connects Herzen Castle to the dark forest on the opposite sides of the gaping hole to the mines that surround the castle.
This gate is the main door into the castle. Layton and Luke meet Parcelle here, but he runs away, terrified at the apparent vampire near-by. Then Nigel invites Layton and Luke into the castle.
The great room is the center of the castle and the largest room inside. There is a huge chandelier inside this room and access to the second floor via large staircases. Anton's sword collection resides in this room as well. The entire duel between Layton and Luke takes place in this room. Fifty years ago, this room was used for large spread dances hosted by Duke Herzen. It is also where the chandelier falls and causes the castle to collapse.
This is the central dining room where Anton and Nigel most likely eat. This room is where Layton and Anton have their first conversation. Nigel is found in this room over the course of the game.
The storage room is found in the lowest of levels of the castle. This room is where Layton and Luke end up after they go into the guest room. Layton and Luke escape this room in search of the answers from Anton and eventually confront him and they solve the mystery.
This is the room that Anton invites Layton and Luke to stay in for the night. This room is just like any fancy room you'd expect in a huge castle. On one of the walls is a very peculiar portrait that piques Layton's interest.
As the name suggests, this is a room that is filled with machinery. Inside is a giant hole that leads into the mines below. Also, this room is the lowest room inside of Herzen Castle.
The secret room is a room that is obviously a secret from those who do not know of Herzen Castle's mysteries. This room holds an entrance to and from the dining room of the castle.