In architecture, a hall is a relatively large space enclosed by a roof and walls. In the Iron Age and early Middle Ages in northern Europe, a mead hall was where a lord and his retainers ate and also slept. Later in the Middle Ages, the great hall was the largest room in castles and large houses, and where the servants usually slept. As more complex house plans developed, the hall remained a large room for dancing and large feasts, often still with servants sleeping there. It was usually immediately inside the main door. In modern British houses, an entrance hall next to the front door remains an indispensable feature, even if it is essentially merely a corridor.