According to Wikipedia, Ouro Preto (from the Portuguese 'Black Gold') is a former colonial mining town situated in the Serra do Espinhaco mountains and designated a World Heritage Site by UNESCO because of its outstanding Baroque architecture.  The town was the focal point of the gold rush and became tremendously wealthy.  In 1789 the city was the centre of the 'Inconfidencia Mineira' a failed attempt to gain Brazil's independence from Portugal.

We drove there from Campos Altos in our trusty Fiat "Attractive Idea" hire car from Localiza (which was a VERY long drive for one day) with no advance knowledge of quite how steep and narrow the roads would be.  We also were unaware that there was a conference taking place, so there were very few rooms available.  However one of the very helpful guides in Praca Tiradentes soon found us a Pousada for our first night, though we had to transfer to another one for the second night - this turned out to be a bonus because we ended up staying in TWO lovely old pousadas, though the drive between them was a little scary.

We visited lots of extravagently decorated churches (one of the churches we visited contained two tons of gold on the carvings and altar!), as well as museums and a gold mine, and needless to say ate more wonderful meals!  If you get the opportunity to visit Ouro Preto, try to find accommodation as close to Tiradentes Square as you can... it is right at the top of the hill and close to the main tourist sites; make sure you have comfortable shoes, and if you want to see as much as possible in a short time, book an accredited Ministerio do Turismo guide with a car to drive you around!

I can recommend the  Arcanjo Pousada (if you're feeling extravagent) and the Pousada Ouro Preto (mid-range)