A guide at a mine I visited told me that at one point part of the city collapsed because they weren't being careful enough in a construction project. She also told me that during big parties and festivals the city has to control how many people visit certain areas of the city because they are afraid the ground could collapse into some of the mines.
Today, you can visit mines in Ouro Preto. The one I visited, Mina do Palácio Velho (Old Palace Mine), is working very hard to think differently about the history of mining. They are very honest about the violence faced by people who were enslaved but also speak to the brilliance of these people. They demonstrate how accurate their mining techniques were and show you how they worked naturally with the land instead of just blowing it all up to find the gold. Black Movements in Minas Gerais and throughout Brazil are constantly doing difficult and brilliant work to expose the truth of the history of slavery in Brazil and challenge the idea that Ouro Preto is just an idllyic. historical city.
In response to the unstable land underneath the city, many organizations now prohibit the exploration of historical mines so as not to cause anymore collapses. You might think this hurts tourism in Ouro Preto, but the city and its residents haved worked to expand tourism beyond just mining. You can visit a daily fair of handmade goods, explore countless museums within a walk from your hotel, and climb various mountains with well marked trails to see spectacular views of the city.
