Prestige for conquering a city, fort, oasis


I was thinking 1,000 prestige for a city (100% if at or above your level; less if it's below your level). Remember, you have to attack the city 10 times and there is a max of 5 times per day so it really is a hard task.
A fort can be similarly rewarded (you must attack 3 times)... perhaps 500 prestige (again, maybe use a sliding scale for different levels). An Oasis is easy to conquer and you get lots of resources so perhaps just 100 prestige (using a sliding scale).
What do you think???