—Millions of surveillance cameras record video around the clock, producing huge video archives. Even when a video archive is known to include critical activities, finding them is like finding a needle in a haystack, making the archive almost worthless. Two main approaches were proposed to address this problem: action recognition and video summarization. Methods for automatic detection of activities still face problems in many scenarios. The video synopsis approach to video summarization is very effective, but may produce confusing summaries by the simultaneous display of multiple activities. A new methodology for the generation of short and coherent video summaries is presented, based on clustering of similar activities. Objects with similar activities are easy to watch simultaneously, and outliers can be spotted instantly. Clustered synopsis is also suitable for efficient creation of ground truth data.