Sub Pop’s Seattle office is plenty nondescript. It’s located above a restaurant in a swank part of the city. There’s no sign on the door. The concierge of my hotel didn’t even know where it was located, and it was directly across the street.

But once inside — up a single elevator to the third floor — you sort of understand why they’ve got to be discreet. If they flew a flag out front, the place would be inundated by excited music geeks like me.

As the label celebrates its 20th (official) year in business, there’s so much history on display here, it’s simply mind-boggling. (For a look back at the label’s history and a list of 21 quintessential Sub Pop albums, check out this week’s Bigger Than the Sound column.) The walls are lined with original mockups for album covers (like Mudhoney’s Superfuzz Bigmuff EP and the banned artwork for Tad’s 8-Way Santa), early design concepts for Sub Pop’s iconic “Loser” T-shirt (complete with handwritten instructions from founder Bruce Pavitt that read, simply, “Make it BIG”) and original Charles Peterson photographs of young bands like Nirvana and Soundgarden. There are Polaroids of Beck, Greg Dulli and Stephen Malkmus clowning around at the old Sub Pop store. And there are gold and platinum records in the bathrooms.

And then there’s the warehouse, staffed by none other than Mudhoney frontman (and grunge god) Mark Arm and overflowing with every rare album the label has released over the course of two decades. The 15-year-old inside me leapt at seeing Saint Etienne CDs I hadn’t even thought about in a decade, and fainted a bit when Arm showed me the original pressings of ‘Honey’s “Touch Me I’m Sick” single. Oh, and there were T-shirts to the rafters. It was magical.

I was lucky enough to be given a tour by Megan Jasper, Sub Pop’s receptionist-turned-VP, who proudly showed off the photo booth and beer machine in the kitchen, joked about the lack of “happy endings” in the office massage room and let me run wild and free in the warehouse, where I grabbed records and generally behaved like an idiot.

Jasper knows all the names of the office dogs, knows how to sneak up to the roof to catch a glimpse of the Space Needle and can explain each piece of artwork and ephemera stuck to the walls. It was like having the world’s greatest tour guide on the world’s greatest tour. It was my indie-rock dream come true. It was amazing.

Oh, and as I was leaving, they even let me take my photo in the booth and stapled the pics on the wall, right next to the guys from Oxford Collapse and below Martha Plimpton. Sometimes I am very lucky.