The Houses of Healing were houses in Minas Tirith at which the healers of Gondor tended the sick and injured. They were located in the sixth circle of the city, near the tunnel to the Citadel, surrounded by lawns and trees. 
War of the RingEdit
The eldest of the women that attended the sick was Ioreth, who cared for many of the wounded after the Battle of the Pelennor Fields, including Faramir who had been wounded by a Southron's arrow, as well as Éowyn and Merry, both of whom had been injured grievously while slaying the Witch-king of Angmar. Aragorn later entered the city as a Captain of the Dúnedain of Arnor, as Faramir was still the Steward of Gondor. Aragorn revealed himself as king after Ioreth said, "The hands of the king are the hands of a healer, and so shall the rightful king be known." He requested the herb Athelas only to be told by Ioreth and the herb-master that they didn't keep any in the Houses of Healing because only the very sick or badly wounded were tended there and they didn't know of Athelas's power. They had to send Bergil to find some. Aragorn then healed the wounded, crushing leaves of Athelas in steaming bowls, to make a healing brew.
When Aragorn and the Captains of the West led their forces to challenge the Black Gate of Mordor, Éowyn and Faramir were left in the care of the Warden of the Houses of Healing, where they met and fell in love. After the destruction of the Ring of Power and the return of Aragorn to the throne of Gondor, they were wed, and Éowyn became Lady of Ithilien.