The Marketplace is a building of the Gondor faction (in BFME 1) and the Men of the West faction (in BFME 2) that provides economy upgrades. These upgrades only are effective as long as the Marketplace is maintained and not destroyed.
Upgrades in BFME 1
Golden Harvest - Cost:
Upgrades in BFME 2
Grand Harvest - Cost: 1500 - Resources coming from Farms are increased by 10%
Siege Materials - Cost: 500 - Other buildings will refund 50% of their build-cost if destroyed by the enemy
Iron Ore - Cost: 1500 - The cost of Forged Blades and Heavy Armor upgrades is reduced by 25%