The Marketplace is a Cultural Building unlocked in Early Middle Ages which provides as high as 430 Happiness, however costs a ton of Supplies to construct it in the beginning which is hefty.
It is recommended not to build this because of its price, but instead a Public Bath, which offers 570 happiness for a lower price,but takes a bit more space, 4x4 instead of 3x3. However, keep in mind, that the Public Bath is not as efficient as the marketplace, in terms of happiness per tile, therefore you should make your own decision.
Efficiency[]
+47.8 per tile.[1]
Other Cultural Buildings[]