I visited the famous Pixar Animation Studios located in Emeryville, California about a month ago when I was in San Francisco for the Summer Expo at the Academy of Art University.
I decided to create a MailArt on the front of the envelope with a Thank You note for my host who invited me to visit this amazing studio that is exclusive to employees only. Only a few people can visit the studio if you know someone from the inside in order to get a tour.
The media I used for this was using a Pentel Pocketbrush Pen, and Copic Markers. This took me about 2 hours from start to finish. It took me times to work on it because the envelope I was using isn't a fan of my tool of choice due to excessive bleeding on the paper.