When Glorfindel was young he would forget, sometimes, that Gondolin was not the only City in the world.
(Ondolindë, they called her then, Ondolindë who dressed herself all in white to match her buildings, Ondolindë with golden skin and a voice like bells. Gondolin, perhaps, if you were of a certain political stripe, but for the most part they called her Ondolindë; everyone knows her as Gondolin, now, the name that Glorfindel who was once called Laurefindel doesn't remember her ever using for herself. Gentle Turukáno is called Turgon now, by those who never knew him, and sweet Itarillë known as Idril; Glorfindel always forgets, until he reads one of the histories, and then is nearly hit in the face with the reminder.)
But regardless, Gondolin is the only City he had ever known, before, and Rivendell is — very different. Quieter. More scarred. Gondolin had only one scar, one pockmark wound from a javelin, until the very end when her skin split and she screamed as she burned; Rivendell's skin is marked all over with wounds from swords and arrows and with bruises that will never heal.
Rivendell uses their Westron name, and has no name in Quenya. Glorfindel has asked if they would rather be called Imladris, and they looked at him with dark eyes and asked why they would change their name, and Glorfindel did not ask again, isn't sure how to explain what he had really meant. He thinks Rivendell understands even so; sometimes they seem to understand everything.
But other times Glorfindel sees them and forgets they even are a City, so accustomed is he to Ondolindë unwounded, who danced with Turukáno in the pale golden light of her lanterns and laughed easily and smiled like she'd never have reason to stop.
He is welcomed into the Third Age and appointed seneschal by Lord Elrond, who looks more like his great grandfather than Glorfindel suspects he knows. The portraits show Turukáno’s high cheekbones and the sharp lines of his face, show how stern his gaze could be; the portraits don't show how gentle Turukáno looked when he smiled, or the tiredness around his eyes, or the way he held his hands when he wasn't thinking about it, or how he carried Itarillë or how he danced with Ondolindë or how he laughed with Aredhel, way back when. Not for nothing do they call Elrond kind as summer here in this new land, and Glorfindel wishes that he had known the phrase back in what he still sometimes thinks of as home.
Glorfindel doesn't mention to Elrond how very like his ancestor he is; he suspects that Elrond has heard it enough. (He is not so blind as to not notice that there are eight pointed stars emblazoned on the buildings of Rivendell. He is not so forgetful as to not remember that the star of Eärendil had six points, not eight. And he is not so tactless as to point any of this out.)
Elrond and Rivendell are — not like Turukáno and Ondolindë; neither of them dances. They sit together, sometimes. Rivendell sits in the Hall of Fire on the nights when Lindir sings; more often than not Elrond will join them, and put his head on their shoulder, and sometimes one or the other of the twins will sit at their feet. Arwen lives with her grandmother in Lothlórien these days, but when she was small she grew up in Rivendell’s lap nearly as much as she did her own mother’s; paths would smooth themselves beneath her unsteady feet just as stairs lowered beneath her brothers’.
Rivendell joins Elrond in the Houses of Healing, joins Lindir in the Hall of Fire, joins Erestor in the library, joins Elladan and Elrohir in the gardens. They don’t conspicuously avoid Glorfindel, but he doesn’t see them often except in passing. They sit in on councils but seldom speak during the meeting itself, preferring to wait until after the meeting is over and they are with only those they wish to be heard by. They sit on the edges of roofs and bridges, knowing with that quiet certainty they always seem to have that they will not fall.
Glorfindel sees Elrond and the City he leads with their heads together and wishes could hear them speak, wishes he had been back from Aman when Rivendell was founded, because — he could give any number of reasons, but it’s because he doesn't understand them, not like he understood Gondolin, or at least, not like he thought he understood her (in death it became very clear to him just how little he ever really understood of anything.)
He knows Rivendell's pathways, has defended them from siege and led their children home from war, witnessed their grieving, and still they are a mystery, this quiet, narrow shouldered City with hair and eyes as black as a Sinda's eyes and skin darker even than any Noldo's he's ever seen. Nothing at all like golden laughing Gondolin who danced in the streets.
He doesn't mention this, of course, to Rivendell or to Elrond or to anyone else.
(The thing about Cities is — there are things they don't say in the histories. There are things Ondolindë's children never saw of her — the sleepless nights with her Turukáno and the sleepless nights without him, Aredhel's terror like a deer before the hunt and, later, Maeglin's trapped desperate clawing fear like a rabbit with its leg caught; the way she smiled and smiled and knew full well it wasn't going to last. The echo of remembered Tirion in her streets, her shining buildings an imitation of a City she never got to meet. The knowledge, never spoken but always present, that once you entered her walls you could never leave them.
Scarred Rivendell with their gentle hands, whose children went off to war and whose first King never returned, who came into life during a siege, knows more peace than Gondolin in her hidden valley who until the very end knew no war ever did, or ever could have.)