I have made this suggestion in another post but I am separating it out and going a little bit deeper into why I think it is a good idea...

The core idea is to add a watchtower to the city military buildings... Place it somewhere in the development structure and allow it to be upgraded like other buildings.  Its purpose would be to see incoming attacks.  Without it the defender would only see incoming sieges and raids at a certain distance (5min?) As tower is added and upgraded the watch distance is increased.

Is it taking a feature away from the game and forcing players to build and upgrade a building to get it back?  Yes and no... for players focused on attacking and raiding other cities the fact that the raid is visible as soon as it is launched creates an increased risk... Launching a real attack from 45 min or 1 hour away is very dangerous with the current system. So attacks will probably start from further away if the feature is implemented and aggressive players would probably welcome the feature and take more risks...

The raid/siege is one of the more interesting aspects of the game. Adding more variability and opportunities for strategy to matter is a good thing as I see it.  Your opinion?