What it is: France’s historic prime meridian, running through the Paris Observatory.
Modern longitude: About 2°20′14.0″ E (≈ 2.3372° E).
Why famous: Used as the official French reference for maps and time into the early 20th century; appears in old atlases and is the basis of the Arago medallions around Paris (often referenced as the “Rose Line”).
What it is: A “zero” meridian used by many early modern European cartographers, running through El Hierro (Ferro), the westernmost Canary Island.
Modern longitude: Around 17°40′–18°03′ W, historically rounded to “20° west of Paris.”
Why famous: Adopted officially by France (1634) as a neutral western line so no one had to use another country’s capital; referenced in older European charts and some historical legal descriptions.
What they are: A set of prime meridians used in the U.S. that run through Washington, D.C., including:
Approx longitude: Around 77° W of Greenwich, with a few arc-minute differences depending on which monument you use.
Why famous: Used as the U.S. “zero” for some 19th-century mapping and for the Public Land Survey System concept of an “American Meridian.” They appear in historical U.S. geodetic work and land descriptions.
What it is: The main Russian astronomical and geodetic meridian, running through the Pulkovo Observatory near Saint Petersburg.
Modern longitude: About 30°19′42″ E.
Why famous: Served as the zero meridian for much 19th–20th century Russian and Soviet mapping, similar to how Greenwich served the British.
Longitude: About 39°49′34″ E.
Why famous: Proposed in modern times as an alternative “Islamic prime meridian” (Mecca Time) and appears in some religious and cultural discussions of timekeeping.
Longitude: About 35°13′47″ E.
Why famous: Appears in older theological/astronomical traditions and sometimes in modern “sacred geography” concepts.
What it is: Zero meridian used in classical Indian astronomy, running through Ujjain in Madhya Pradesh.
Longitude: About 75°47′ E.
Why famous: Mentioned in the Surya Siddhanta and used for centuries as the reference for Indian time and calculations — essentially an ancient regional prime meridian.
A number of countries historically used their capital city as a local “zero” meridian.
Use: Employed in Qing-era Chinese astronomy and cartography.
Longitude: Approximately 116°24′ E.
Use: Used on 18th–19th century Japanese maps (officially 1779–1871).
Longitude: Approximately 136°14′ E.
Similarly, there were historic Lisbon, Madrid, Florence, Amsterdam, Oslo, and Warsaw meridians, each through their observatory or a key public building. These were “famous” mainly within their own mapping and time-keeping systems.
What it is: The Treaty of Tordesillas established a dividing meridian in the Atlantic to split the non-European world between Spain and Portugal.
Approx longitude: Later reconstructions place it about 46°–48° W of Greenwich (depending on the reconstruction).
Why famous: Known more as a geopolitical boundary than as a scientific prime meridian.
What it is: The exact International Date Line zigzags for political reasons, but its conceptual backbone is the 180° meridian opposite Greenwich.
Why famous: It’s where the calendar date effectively jumps by one day, not a traditional mapping zero but a critical time-keeping boundary.