After collecting first three Light Seeds go out through the main door and start collecting balls situated just over the banister surrounding the tower.
Go inside again and start climbing up in the direction of a balcony presented on the picture.
Go to the terrace and run around the tower. Then slide down trough a hole in the floor.
Collect all Light Seeds situated here and jump to the corridor leading to the Royal Spire.
First collect all Light Seeds situated on the right side. Collect the rest on your way back.
30 and the following - on your way to the City of Light.
36 and the rest on the way to location the Ahriman's Tower.
If you have Wings of Ormazd ability, jump onto yellow Power Plate in a place where you are going to teleport yourself.