We describe the development of a robust, self-sustainable, versatile environmental monitoring station, the S3ME2, with a multitude of sensors capable of operating in extreme environments (from cold arid sub-arctic regions to hot deserts and high-altitude mountain terrains), providing realtime quality data of critical climate and geophysical parameters for a wide field of research such as pressure, surface and subsurface temperature and humidity, magnetic field and seismic activity. The dedicated communication modem utilizes IoT technology and can deliver this data from remote regions. The S3ME2 has been designed as a low-cost instrument to facilitate the production of multiple units. During the pilot phase, it has demonstrated continuous operability for up to 6 months, including survival during extremely cold, snowy, and low insolation, and low wind periods in the Sub-Arctic region. With its robust design, S3ME2 exploits the use of renewable sources of energy such as solar and wind power to power the system. The S3ME2 has also been designed from a modular point of view with commercial off the shelf components (COTS) and open source hardware, considering long term operability of the station. The sensor modules can be easily added, replaced, or upgraded such that a stable functioning of the system is guaranteed.