While I cannot remember the name of either module, I remember two different setups that would work quite well for an inn as being a nexus of adventure.
In one, there were paintings in a hall that lead to other places. The paintings could be far regions the characters travel to and the outward to adventure from there or could be adventure spots themselves. As I remember, there was some way to charge the system either through a ritual or the application of magic spells/items to be drained to power the portals.
My addition would be that if you wanted to go further with it, the innkeepers son/daughter/whatever could be creating the paintings. Each painting leads to some trouble in the world that needs to be solved (i.e. an adventure). After a time, the painting stops working, which prevents them being used to create an intercontinental trade network. (Which is basically what my players were aiming for with the adventure with the hall full of paintings permanently going to locations.)
The second example I remember was an inn that had a well which lead down into a famous dungeon. I remember seeing information about the rates the innkeeper charged for adventurers to go down into the depths. I think this was an actual WoTC product, but right now I cannot remember what.