Kyanite Circles

When Calvaria was nothing but an island city they didn't need to create much in the way of travelling arcane methods.
However when the Dragons wanted more it drove the city to ambition and conquest.
Led by the House of Kyanite the dragonkin took up blade and the arcane.
Marching out across most of the known world Calvaria, the City of Dragons, conquered and established towns and ports as there own.
The larger the empire got the more they needed to find a way to travel across it with ease. Practioner's of the magical arts spent decades on research into spells that could be used to take armies from one place to another.
With such a need the Calvarian's managed to create a spell that would allow the caster to teleport to a destination they had visited before. Many failures and fatalities were endured before success.
At the birth of it that was all it could do. But it developed into allowing the caster to bring chosen allies to the target destination. But it left a mark, a pattern of arcane writings.
If this pattern was committed to memory then the caster could teleport to it regardless of ever having been there before. Even now it can still go awry but the more one practices it lessens the odds of a mistake.  
When the draconic empire fell apart and the natives of the lands took back their home much of the Calvarian presence was cast out. However these arcane teleporting circles were kept.
Present day the teleportation circles are used often and they led to the development of other magics that enabled arcane travel.
Planar travel, both demi and pocket. Trade with the elemental realms and the like became possible.
Due to the Calvarian Empire, it now meant many realms could communicate and visit for a plethora of reasons.