Copyright (c) 1978 Robert Moore 

This game is played on an empty 10x10 square board (also called the city):

Each player starts with two sets of 11 pieces each (the last piece represents the cathedral which is unique and does not belongs to either player):

SETUP - One player drops the cathedral on the board. The other player starts.
TURN - On each turn, each player passes or drops one of his pieces on a set of empty cells (the piece may be rotated).
Claiming Territory - If a player completely surrounds an area of the city (with his pieces and the city edges - only orthogonal connections are valid!) that part of the city is owned by him. The opponent may not drop pieces in there. 
It is not valid to claim territory on the first turn.
The Cathedral may not be used to surround areas.
If a player surround one and just one opponent building or the Cathedral, he may remove the surrounded piece and claim that territory.
Surrounding in this context, means that the figure is alone on an area that would be immediately claimed by the player if the captured piece was not there.
The surrounded piece (except the Cathedral) may be dropped again by the opponent on a later turn.
GOAL - Wins the player that drops all of his pieces. 
The game also ends when both players pass. Then, the winner is the player with more stones (each piece is made of several stones) on the board.
An example

I alternate the use of marked and non marked stones to better show how the different pieces were dropped.  

The top left area was claimed by Black, White cannot drop there.

Even if Black surrounds the bottom left area, the white T is not captured since it shares that area with the Cathedral (so there are two pieces). That area may not be claimed by Black.

The top right corner is not claimed by Black because one connection is diagonal (h9-i8), which is not valid for surrounding purposes.

If White drops his next piece on the green dots, he will capture the bottom right black piece. Then, he claims that area.

The original rule set suggests some tactics: (a) Concentrate on claiming space in the early stages of the game; (b) Play your largest buildings first; (c) Be careful not to let any of your building get captured; (d) Never play your buildings into your own space while there is still unclaimed space available; (e) Never give up until the last building is played.