And do not forget the various military ship tunnels out there. https://en.wikipedia.org/wiki/Naval_museum_complex_Balaklava https://en.wikipedia.org/wiki/Naval

And do not forget the various military ship tunnels out there. https://en.wikipedia.org/wiki/Naval_museum_complex_Balaklava https://en.wikipedia.org/wiki/Naval_museum_complex_Balaklava https://www.cnn.com/2020/08/21/asia/china-submarine-underground-base-satellite-photo-intl-hnk-scli https://www.cnn.com/2020/08/21/asia/china-submarine-undergro...