Akihabara Radio Kaikan

Akihabara Radio Kaikan, often shortened to simply Radio Kaikan, is a building in Akihabara, and is a key location in both Steins;Gate and Steins;Gate 0.

Steins;Gate
Radio Kaikan acts as the starting point for the story. It is where Rintaro and Mayuri attend Dr. Nakabachi's conference and Rintaro first meets Kurisu. It is also the location of Kurisu's eventual death in the Beta Attractor Field.

In the Alpha Attractor Field, a satellite crashes into the building, destroying the room Dr. Nakabachi was going to speak in. This event causes Nakabachi to cancel the entire press conference and the police soon close the building and surrounding area to the public. Later on, Suzuha takes Rintaro and Kurisu to the building and explains that the satellite is actually her time machine. Suzuha had attempted to land on the building's rooftop, but a miscalculation lead her to crashing the time machine into the side of the building. Rintaro, Kurisu, Mayuri, Itaru and Suzuha then gather there to help repair the machine over the next several days. Suzuha eventually leaves, leaving an empty hole in the building for the rest of the story in this Attractor Field.

Back in the Beta Attractor Field, in August 21st, Suzuha lands successfully on the building's rooftop and calls Rintaro there.

Steins;Gate 0
The final confrontation between Stratfor, DURPA, and Russian intelligence takes place on the roof and the disappearance of the time machine on top of the building is one of the convergence points that leads to WWIII.