You're searching for a magnetic nano cache of the usual sort in a likely location. The spot was chosen for the 10 year anniversary of what you'll find located just before the entrance, a favourite treasure hunting place for us on the weekends. The difficulty rating reflects the high chance of being caught if you attempt this on a weekend--the hide itself should be fairly obvious.
Hint and cache updated due to the constant tagging and vandalism. Cache is a nano now and please bring a pen and some kind of extraction tool, it can be challenging to get the log out. I had a challenge to get it out
A trackable is available to be found on Saturdays between 9am to 5pm. Take a stroll inside the market and look for Vance the Minifig Explorer amongst his other minifig friends in a stall holder's collection!