Single Graves are located all over Tibia and are different than big graveyards. This page lists a few single graves, but is rather incomplete.

Mainland

Grave inside Dusalk's Troll Clan Cave

You see a grave.
You read: Deraut kadet ul al cadert!
Herot kar Gurxat

Grave in Undead Crypt between Kazordoon area/Mount Sternum Undead Cave

You see a grave.
You read: Orin Lochlinn
R.I.P

Graves in small area on mountain The Big Old One/Kazordoon (area of The Paradox Tower Quest)

You see a grave.
You read: ??

Grave in surface of Ghostland (part of the The Queen of the Banshees Quest)

You see a grave.
You read: In honor of those, killed for a kiss

Grave in surface of Plains of Havoc (part of the The Demon Oak Quest)

You see a grave.
You read: Yesim Adeit

Below Necromant House (The Grave of Goshnar)

You see a grave stone.
You read: GRAVE OF GOSHNAR
the necromant king
ESRO ILEM NITBIT
ALS URUKH ASHARAK THAI
EXURA RES VITA UTAMO MORT

Premium Areas

Grave in a cave under Treasure Island:

You see a grave stone.
You read: See what you have done! Be
cursed, worst Navigator of them all

Grave between Zao's Dragonblaze Peaks (part of the An Uneasy Alliance Quest, here)

You see a grave.
You read: Here rests Mooh'Tah master Svorus

Grave north of Vengoth

You see a grave.
You read: Shut your eyes
Kiss me goodbye
And sleep

This grave's text is an allusion.