The Carlos III University of Madrid is a young institution, created in 1989. It is one of the top universities in Spain, with almost 20,000 students and a strong international profile. More info here.
In the ranking QS Top 50 Under 50 2015 for the 50 best Universities created in the last 50 years, Carlos III appears number 33.
Regarding the Social Sciences, the Carlos III University offers undergraduate degrees in Economics, Sociology, Political Science and International Studies, as well as a number of graduate programs. There is a strong Department of Social Sciences and several research institutes, including the IC3JM.