Aerial view level design Thread

I've recently began making a top view (like Pokemon or Legend of Zelda) that's part dungeon crawler, part open world. How do I begin making dungeons or levels?

What program are trying to work with?

If you were going for something super simple id use a simple 2D/2.5D game engine such as RPG Maker VX Ace or Game Maker Studio for the game, depending on what kind of game it is.
If your looking on how to make a level/room, start with an entrance and exit(s), then think what can I do to make it difficult/interesting to get through the room. Are there certain things I as a player need to get to, information, items? Were in the world would they be located? Am I on a free roaming adventure were I can go anywhere or will I be confined to certain rooms until I complete a certain objective?
If you want to know how to actually draw the level in a program, start with the most prevalent texture. So if the room is mostly grass, fill it with grass. Afterwords block out were all the big objects in the room will be such as buildings, walls or mountain sides. Then go for smaller details, such as paths through the grass, and then save all the very fine details for the end such as all the textures that show off the individual blades of grass or the broken tile in the floor. Keep in mind you should keep each set of details on a separate layer so you can back and edit them easily if need be.

Hope these help.