Is there any famous treasure related with the gods of Norse mythology? Something like a famous vault or maybe cave. An accumulation of important things that they wanted to protect, for instance.
The Norse gods of the sagas don't seem to have accumulated treasure in caves or chests, but they had many marvellous items, mostly made by the dwarfs. They included Frey's ship, Skíðblaðnir and boar, Gullinbursti, Odin's spear Gungnir and ring Draupnir, and Thor's hammer, Mjölnir.
If you are looking for archaeological evidence of Norse/Viking (unfortunately, the terms are often used interchangeably) religious practices, then there are a number of academic papers available online (for example, this one titled Evidence of the Viking Religion Through Archaeology). Much of that evidence comes from grave goods (like miniature Thor's hammer (or, "torshammere") amulets), deposited in Norse/Viking burials, but there are also several examples of carved monuments and standing stones (like the Ardre stones from Gotland) that depict aspects from Norse Mythology.
Many pagan "cult" sites associated with Norse/Viking mythology have been discovered in Scandinavia. A good example is the temple site at Gamla Uppsala, where archaeological investigations have revealed the remains of the temple dedicated to Thor, Odin, and Freyr.
In the case, of the temples at Gamla Uppsala, we have an account of how the temple actually appeared in the 11th-century in Adam of Bremen's Gesta Hammaburgensis ecclesiae pontificum. It is perhaps worth mentioning that Uppsalla was also described as being the domain of Freyr in the Ynglinga Saga. A number of translations of the Ynglinga Saga are available online, for example here.
Look up the treasures forged by the dwarves of Svartalfheim in their competition to please Odin and Thor and the other gods (the myth in which Loki bets his head, loses, then famously gets his mouth sewn shut).
Of the treasures created by the dwarves, I'd guess the most valuable monetarily is Odin's ring, because it multiplies every few days and he's presumably been around for thousands of years... I've not read anything on what he did with all his extra rings. If this is for a creative writing project, maybe you could extrapolate that he's got them all locked away in a chest somewhere.
The more valuable (non-monetarily) treasure, I think, is the ship because it is so useful and yet so concealable. And as far as real-life Viking relics merely related to Norse myth, I think something along the lines of Mjolnir would be your best bet. Vikings really did use warhammers and several relics like amulets representative of Thor's hammer have been unearthed.
But, if you want a real treasure important to most or all of the Norse gods, I'd focus on Idun's Golden Apples. In Norse myth, they grant immortality to the gods and are kept by a specific person (Idun, pronounced ee-done), and the magic fades when Idun is taken in another story...