Because I like to be the extra boards to stay a special attraction, I changed the rules about moving between them a little:
There is no direct way from the main board to the other boards. The only way to get there is due to adventure cards. This could be i.e the Dungeon Entrance, the Landslide or the Warp Gate. You can also move through Runegates: They will teleport you (as written on the card) to the Runes or to another Runegate, but you can also decide to move to a random starting point of another board. This also works between outer boards.
The City board works a little different: Anytime a player lands on the City space of the main board, you roll a d8: on a 7,8, the city opens its gates, and the city board can be entered from now on as written in the rules. Of course the City space of the main board can be visited as normal all the time.
To make it a little more interesting, I introduced opening hours for the city´s locations.
As soon as the City opens its gates, roll a d6 for each shop:
2,3 : open 24 hours
4-6: if Rogues Guild, Soothsayer, Magic Emporum, Sorcerer, then open only at night
if Stables, Menagerie, Armory, Apothecary, then open only at daytime
Academy and High Temple:
1,2 : open 24 hours
3,4 :open at daytime
5,6: open at nighttime
I usually use fate tokens to indicate the openings hours: gold for day, silver for night.