If you want to see what's actually inside the file before loading it into Minecraft, you can: Use a tool like 7-Zip or WinRAR to open the archive.
: Use Spectator Mode ( /gamemode spectator ) to fly through the terrain. Map makers often leave "signed" rooms or developer notes far away from the main path. BB_BestDayEver.zip
Custom maps of this style often hide in unexpected places. If you want to see what's actually inside