METROS
| Date | Clue |
|---|---|
| 2025-08-28 | Some underground networks |
| 2025-02-15 | London and Budapest have had them since 1863 and 1896, respectively |
| 2024-09-19 | Population centers, informally |
| 2024-05-24 | Urban areas, informally |
| 2019-06-06 | Underground networks |
| 2018-07-04 | Subways |
| 2014-08-31 | Subway systems |
| 2011-09-07 | Some urban transit systems |
| 2009-08-02 | Urban railways |
| 1998-02-01 | Underground systems |
| 1995-04-02 | Subways |