El Born Centre de Cultura i Memòria is sixty streets of the city as it stood in 1714, kept under an iron market roof. Below the walkways lie the streets of the Ribera quarter: house walls, wells, drains and cellars, the floor plans still legible five metres down. You cross above them on a raised deck and look into the rooms. Nothing was built on top, and that decision took eleven years of public argument to reach.
What you are looking down at was emptied on purpose. Barcelona surrendered on 11 September 1714 after a siege of more than a year in the War of the Spanish Succession. Philip V, the new king, had about a thousand houses in this quarter pulled down and their residents moved out, and a fortress went up to hold the city. Catalonia's own institutions were abolished by decree soon after. The ground was then left alone for nearly three hundred years. When the centre opened in 2013 the day chosen was 11 September, so the streets below were reopened on the anniversary of the morning they were lost. Look down from the rail and pick a doorway; somebody was told to leave it.