Memento Mori

Memento = (“remember!”), imperative form of memini (“I remember”).
Mori = verb - present active infinitive of morior (I die)

memento mori = "Remember your mortality", "Remember you must die" or "Remember you will die"

Ancient Origins

When a Roman general had won a particularly spectacular victory, he was given a triumph. He would parade his army through the city itself, normally taboo in Republican Rome, and he would display the loot and slaves he had won.

He rode a chariot, and stretched out in front of him marched the senate, musicians, exotic animals, white bulls for slaughter, and captured enemies. Upon his head was a crown of laurel leaves, and all around him the populace cheered his glorious achievement.

By tradition, though, a slave rode behind him. Every once in awhile, the slave would whisper this into his ear:

"Memento mori."

Remember, you too are mortal.

Perhaps the most famous memento mori from ancient times comes from Greece, rather than Rome. It is said that a monument was placed at the pass at Thermopylae, where the 300 Spartans fended of a million Persians and saved Western Civilization. A Spartan of course was to come home with his shield or upon it; victory or death, in other words.

Inscribed in the stone was a poem which served to remind the living of this stark practice. It read:

"Go tell the Spartans, stranger passing by, that here, obedient to their laws, we lie."

Mappa mundi

Mappa mundi (Latin [ˈmappa ˈmʊndiː]; plural = mappae mundi) is a general term used to describe medieval European maps of the world. These maps range in size and complexity from simple schematic maps an inch or less across to elaborate wall maps, the largest of which was 11 ft. (3.5 m.) in diameter.

The term derives from the Medieval Latin words mappa (cloth or chart) and mundi (of the world).

Hereford mappa mundi

The Hereford Mappa Mundi is a mappa mundi, of a form deriving from the T and O pattern, dating to ca. 1300. It is currently on display in Hereford Cathedral in Hereford, England. It is the largest medieval map known to still exist.

(note the orientation to the east at the top)

0 - At the center of the map: Jerusalem, above it: the crucifix.
1 - The Paradise, surrounded by a wall and a ring of fire.
2 - The Ganges and its delta.
3 - The fabulous Island of Taphana, sometimes (possibly mis-)interpreted as Sri Lanka or Sumatra.
4 - Rivers Indus and Tigris.
5 - The Caspian Sea, and the land of Gog and Magog
6 - Babylon and the Euphrat.
7 - The Persian Gulf.
8 - The Red Sea (painted in Red).
9 - Noah's Ark.
10 - The Dead Sea, Sodom and Gomorrha, with River Jordan, coming from Sea of Galiliee; above: Lot's wife.
11 - Egypt with the River Nile.
12 - River Nile [?], or possibly an allusion to the equatorial Ocean; far outside: a land of freaks, possibly the Antipodes.
13 - The Azov Sea with Rivers Don and Dnjepr; above: the Golden Fleece.
14 - Constantinoples; left of it the Danube's delta.
15 - The Aegean Sea.
16 - Oversized delta of the Nile with Alexandria's Lighthouse.
17 - A person skiing.
18 - Greece with Mt. Olymp, Athens and Corinth
19 - Misplaced Crete with Minotaur's circular labyrinth.
20 - The Adriatic Sea; Italy with Rome, honored by a popular heptameter: Roma caput mundi tenet orbis frena rotundi [Rome, the head, holds the reins of the world].
21 - Sicily, and Carthage, opposing Rome, right of it.
22 - Scotland.
23 - England.
24 - Ireland.
25 - The Baleares.
26 - The Strait of Gibraltar (the Pillars of Hercules).

"Hereford’s mappa mundi is many things — an encyclopedia of all the world’s knowledge, a memento mori, a remarkable piece of medieval art. It remains a unique testament of a vanished world and a vivid illustration of the depth, complexity and artistic genius of maps themselves.”

http://www.brainpickings.org/index.php/2011/06/29/bbc-the-beauty-on-maps/