One of the original scenarios in Heroes of Might and Magic III, Titan's Winter, contains a strange map structure on the final piece of land, the "Market of Time". This is the only scenario containing this structure, and when I visit it with my hero, nothing happens. What is it supposed to do, or is it just something akin to an Easter Egg?
According to several different wiki pages (like this) it was supposed to allow heroes to unlearn skills:
Market of Time appears to have no function, however it was intended to let visiting heroes to unlearn secondary skills.