Entry: Rift Healer and Mounts
As you run up the path to Meridian, you'll notice the tiered stairs and ramps. Just outside is a tent, the Spirit of Rhaza'de. You'll find the Bard soul quest in here; Elyese is the only soul quest NPC for the Defiants who is not located inside of Meridian, and can be quite a source of frustration.
Go up the stairs and ramp and you'll find yourself in an open courtyard. There are three arched openings and the shape of the city is like an L, with the entry facing into the apex. Head toward the left, southern part and you'll see the Warrior trainer in the Training Yard. He's near the Pyromancer, Warlord, Paladin, Riftstalker, Nightblade, Void Knight, Riftblade, Ranger and Marksman trainers. Wait, why is the Pyromancer here? Hmmm..
Run back toward the middle, or north section, and you'll see Rei Tilkanos. She's a Healer, just in case you're running at less than full power. There's a mailbox on the opposite side of the path from her along with the mount merchant and his stable of Vayiuus and Eldritch Steeds. Just beyond them, to the east, is the Elementalist trainer. Go ahead and enter the inner courtyard through the middle arch.
Epoch Plaza: Rift Auction House and Banker
The same "three arched entries into an L shaped area" is repeated here. This area contains three roofed pavilions and a Porticulum. You'll want to talk to the Porticulum Master to gain the Soul Recall ability and bind your soul to this location. You can now recall back here once per hour. The small area beyond her houses the Dominator and Chloromancer trainers. The northern-most pavilion houses generic Rogue, Mage and Cleric trainers. Directly south of that, a Banker resides in his own pavilion. Moving southeast from there, you'll find an Auctioneer, with the Cabalist and Sentinel trainers hanging out casually nearby.
The small area behind that southern-most pavilion contains the trainers for the Saboteur, Beastmaster, Druid and Necromancer souls, three of whom are arguing about which types of pets are best. Along the back wall of Epoch Plaza, you will find a number of trainer and merchant kiosks. Moving from the south and curving along toward the north, you'll see the Master Butcher, Ranged Weapon and Potions vendors, Master Forager, Drinks Vendor, Master Miner, and the Artifact Collector. Make sure to visit her whenever you have completed a collection. Just past, you'll find armor, drinks and a dye vendor.
Catari Command Center: Rift PvP and Token Merchants
Take the far right, or northeastern arch into the building to find PvP Central, otherwise known as the Catari Command Center. Here you'll find merchants that exchange your dungeon and PvP tokens for gear. Down in the Pit are the trainers for the Bladedancer, Reaver, Shaman, Champion, Paragon and Assassin souls, pretending to duel it out. There is a Warfront Master at the rear of this area. Head back out to the Plaza, and enter the middle arch into the building.
The Foyer: Rift Guild Magistrate and Orphiel’s Spire
Just inside this area is the Guild Charter Magistrate who will sell and register your guild charter, as well as offer you additional guild items. In the middle is a portal-style elevator for Orphiel's Spire with controls to take you up or down by a level. The Stormcaller trainer stands behind the elevator in the rear of this area. There are also ramps on either side, one might assume in case the elevator goes on the blink.
Take the portal up by two floors to find the Archon and Warlock trainers. Go up one more for the Purifier, Justicar, Inquisitor and Warden Trainers. Keep taking the "Up" option until it is no longer available. You'll have to run up the ramp for the very top of the Spire where you find Orphiel Farwind himself, the founder of the Defiant. Now head back down to the portal-vator and take the "Ground Floor" option. We have one more area to explore. If you're a little lost, the way back out to the Plaza is behind the Guild Charter Magistrate.
The Manufactory: Rift Crafting and Professions Trainers
Find the arch leading into the building in the southern-most part of the Plaza, and you'll be in the Rift crafting and profession area of Meridian. There's a Planar Augment Merchant just inside the door if you have some Planarite to spend. To your left is a mailbox, Banker, and Auctioneer, as well as vendors for Runecrafting and Artificing recipes. The vendors selling Armorsmith, Weaponsmith, Apothecary and Outfitter recipes are on the opposite side of the doorway.The lower area holds a Workbench and Loom, along with the Master Artificer, Runecrafter and Outfitters. The upper, northeastern side holds Forges and the Master Weaponsmith and Armorsmith. In the upper rear of this area, you'll find the Laboratory and the Master Apothecary trainer.
Now, look on your mini map and note the extended area from the left side that reaches down to the southwest. Find the path and enter that area. This is the College of Planar Studies, and stepping in here should garner you the "All Things Defiant" achievement, if you don't already have it. Here you can purchase a new Focus or other goods from reputation vendors.
That concludes your walking tour of the Defiant capital city, Meridian. While you're exploring, be sure to pick up any sparklies you see. The books you discover can be added to your collection and then read at your leisure, and they all provide insights to the lore of Rift.