Only the Trading Center. You can sell the rest of the buildings if you no longer need them for production. Here are the last few quests for that chapter:
80 Produce Beverages 20 times. Produce 10 Bread. Produce Basket of Groceries 5 times - 2x Inspiring Meditation spell
81 Gain 60,000 Unurium 200 Diamonds
82 Sell your Trading Center - - 50,000 Magic Dust
83 Invest 100 Knowledge Points in an Ancient Wonder of another player - 2x Ancient Knowledge 15
84 Give Neighborly Help 50 times - 5x Ensorced Endowment