if you have like a bird or something, check the Through box down in the bottom left (where it's got Move Animation, Stop Animation, etc). Then your event will be able to go over water, buildings, trees, etc.
If you don't want it to go over ALL impassable tiles, then investigate the Through ON/OFF options that are in the Set Move Route command - you may be able to use conditions to say which tiles your event should override passabilities on.