In recent years, I've really been enjoying what I consider the "second cities" of Europe. The Chicagos of Europe don't get a free ride, and they lack the blockbuster attractions and charming sights that bring everyone to the big-league cultural capitals. These "second cities" often have a rough, Industrial Age heritage that dug them deep into a rust-belt hole with the coming of the Information Age, but enabled them to be honest, unvarnished, and nonconformist. My list of European "second cities" includes Porto in Portugal, Naples in Italy, Marseilles in France, Hamburg in Germany, Antwerp in Belgium, and Glasgow in Scotland. I find all of these much-improved lately -- underrated and great to visit. (Yes, Glasgow's population is bigger than Edinburgh's. But given that Edinburgh is the capital and dwarfs its rival from a tourism perspective, this travel writer considers Glasgow an honorary "second city.")
In part because of my love of Edinburgh and in part because I don't get to Scotland much, I've never seriously considered Glasgow. I thought I'd like it because I liked the Andy Capp cartoon, which I thought was set here. But when I got to Glasgow, I found out that Andy actually "lived" in Newcastle (south of the border, in gritty North England).
But with or without Andy Capp, Glasgow has a wonderful energy. And, being less an hour from Edinburgh by train (with four trains per hour), it's an easy day trip. I'd say your best "day three" in Edinburgh is to side-trip here for "day one" in Glasgow.
Midway through a very full morning with my guide, Colin, I stopped for a coffee. The busker across the street had charisma, and the people-watching was endearing. Just as I was thinking, "This is so great...where are the Americans?", two women burst into my video to tell me they're taking one of our tours.
Enjoy two minutes with an extra-hot latte on what I think of as "the Ramblas of Glasgow": Buchanan Street.