Slate Mountain Lodge hotel has opened in Blaenau Ffestiniog, Gwynedd, but will not be taking bookings until later this year.
The hotel is owned by the Greaves family, who also own the Slate Caverns visitor attraction nearby, and opened this month to host an engineering firm engaged to carry out maintenance on Llechwedd's hydroelectricity infrastructure, which will occupy the entire hotel until January 2020.
The hotel will have a public launch in spring 2020, after a refresh aimed at making the hotel four-star status. Bookings will go live later in 2019.
The 24-bedroom hotel will serve guests visiting the Slate Caverns heritage and adventure hub. The venue will also have wedding and events facilities, a restaurant and bar showcasing local produce, and the hotel's fixtures and furnishings will have "a distinctly Welsh feel".
Already employing a team of six, the hotel will generate 23 new jobs when it opens to the public. The development has been part-funded by the Welsh government.
The restored 19th-century mountain lodge was home to the Greaves family, who owned the caverns and mine for more than 150 years until the 1970s, and was subsequently used as offices for the mine's managers.
Michael Bewick, managing director of the Slate Caverns, said: "Our beautiful new hotel is part of a £1.5m investment programme which got underway with the launch of our luxury glamping lodges last spring… To bring back to life a building which played such a significant part in Welsh history is wonderful thing, it adds a very authentic extra dimension to the visitor experience."