In recent years terrorists have increasingly targeted multiple highly populated areas within an urban core with the most recent one being in Paris, France. The reasons for coordinated attacks in dense urban cores are many, including media coverage, mass casualties, security force dispersion/distraction and instigation of fear to name a few. Beyond the short to medium term effect these attacks have on the population and real estate assets, terrorists use their networks through a dense core for concealment, preparation, scouting for potential targets as well as shortterm sheltering. The paper analyzes previous attacks, identifies lessons learned and provides various proactive recommendations. It also raises certain concerns especially in light of the significant inflow of illegal immigrants and those claiming refugee status across Europe who are petitioning asylum, which may not be granted. A possible denial of asylum will create significant tensions within the established and non-established holding areas of these masses with possible spoil over effects in urban cores.