In this paper, a “3D taxi that connects high-rise buildings” is proposed. It is an advanced idea that can effectively utilize the 3D space of a city and increase the efficiency of the movement of people and goods. This proposal has the potential to contribute to reducing urban congestion, saving travel time, and improving energy efficiency. The following items are possible examples of applications: (1) a transportation network connecting high-rise buildings within the megacity (for example, Shinjuku Subcenter, Marunouchi, and Roppongi Hills can be connected in three dimensions) and (2) linking buildings such as hospitals, research institutes, and pharmaceutical companies (connecting adjacent buildings will create an evacuation route in case of an emergency). The basic technology is a 3D elevator, which can move not only up and down (vertically), but also left and right and forward and backward. If such elevators are connected among multiple high-rise buildings, people and things can move three-dimensionally and efficiently, without relying on conventional ground or underground transportation. In the future, the introduction of image sensors will be essential. In this study, a model of this 3D elevator is proposed as a “3D taxi”, and an example of how this concept can be used to move people and things to their destinations is indicated.