Where is the mistake? in the xml?
Doesn't it work like this? I want the Colossus to build one free harbor in each city.
Is this possible, will there also be a harbor in a city that is not connected to coast?! 
And another problem: In tech tree, Engeneering AND Physics both show enables bridges over rivers
... I want to have bridges on physics
Thanks for your help.
Doesn't it work like this? I want the Colossus to build one free harbor in each city.
Code:
<Buildings>
<Update>
<Where Type="BUILDING_COLOSSUS"/>
<Set FreeBuilding="BUILDINGCLASS_HARBOR"/>
</Update>
</Buildings>

And another problem: In tech tree, Engeneering AND Physics both show enables bridges over rivers

Code:
<Technologies>
<Update>
<Where Type="TECH_ENGINEERING"/>
<Set BridgeBuilding="false"/>
</Update>
<Update>
<Where Type="TECH_PHYSICS"/>
<Set BridgeBuilding="true"/>
</Update>
</Technologies>
Thanks for your help.