More than 4,000 syringes and bags of human waste have been removed from six problem houses bought by Derby City Council on compulsory purchase orders.
The homes, in the Leopold Street and Arboretum Square area of the city, are the first to be bought by the city council from failing landlords.
A public inquiry agreed the compulsory purchase could go ahead and the houses are now being refurbished.
Nearby residents have protested about conditions in the area for years.
Pensioner Josephine Rooney was jailed in 2006 and 2008 for not paying her council tax in protest at the rundown conditions in that area of the city.
The properties have been leased to a local housing association which is carrying out the clean-up operation.
Councillor Philip Ingall said: "Not only are such properties a waste of potentially good homes for Derby residents, but they can impact heavily on local neighbourhoods by attracting anti-social, and often criminal, behaviour - for instance, more than 4,000 syringes, and many skip loads of accumulations and human waste had to be removed from the Leopold Street properties.
"These are the first houses that we have compulsorily purchased as a direct result of poor management by a private sector landlord - but they will not be the last."
Sgt Nick Allgood, from the Derby city centre safer neighbourhood policing team, said: "This is a very positive step from the council and we hope that it will make a significant difference to the area and to the residents of Leopold Street."
A public inquiry into proposed compulsory purchase orders is held if tenants or landlords object.