Let's bump the old question!)
When playing build cards:
Each player may choose a building
with a value equal to or lower than
the number of cards played.
He then puts the building on
a free space of his player board.
So just after you (let's say 1st player) played the cards you MUST take a building and place it. After everyone else has done that, you decide who has the most cards:
Bonus for most cards played:
The player adds +1 to the number of cards played.
Then it means that the winner MAY return that just taken building and take the more valuable? This sounds a little strange.