There's some 200MW capacity (only 80MW is currently used or being built) data center in a mine near a fjord in Norway. The limiting factor for its capacity seems to be the capacity of the electricity net nearby (which you can just hit and the DC is useless). With how NIMBY Norwegians are there's no way it would ever get to a GW or more even if it might be both technically and economically feasible. That's just one project and can't be replicated anywhere else. It's just a massive advantage that above ground datacenters are relatively 'figured out' and similar everywhere.

edit: 61.9340107, 5.5084207 are the coordinates

Do you know if that 200MW figure is total power budget for the facility (including electricity used for cooling systems and other facilities-support systems), or up to 200MW of electronics loads generating heat? The latter would be something like 300 cabinets with 5-6kW heat each.