What was the dwelling place for monarchs, nobles and merchants?

If we consider the period of the Middle Ages, then the monarchs lived mainly in palaces or castles. Usually, if the city was completely fortified with a fence, then the monarch had a luxurious palace. If it was necessary to secure him even more, then he lived in a powerful medieval castle, also in luxury, but it was quite difficult to take by storm. As for the nobles, they lived less luxuriously, but also in palaces. But the merchants lived in ordinary houses, but much richer than the same peasants, in addition, merchants were often on the road.