Subterranea are underground structures, both natural (such as caves) and human-made (such as mines).[citation needed] Some subterranea and related topics include:
Subterranea are underground structures, both natural (such as caves) and human-made (such as mines).[citation needed] Some subterranea and related topics include:
Man-made and man-related Subterranea | |
|---|---|
| Natural features | |
| Civilian features |
|
| Military features | |
| Mining, quarrying, and underground construction | |
| Related topics |
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| National libraries | |
|---|---|
| Other | |
