Recogito 2 is an open source annotation tool currently under development by Pelagios, an international initiative aimed at facilitating better linkages between online resources documenting the past. With Recogito 2, we aim to provide an environment for efficient semantic annotation—i.e., the task of enriching content with references to controlled vocabularies—in order to facilitate links between online data. At the same time, we address a perceived gap in the performance of existing tools, by emphasizing the development of mechanisms for manual intervention and editorial control that support the curation of quality data. While Recogito 2 provides an online workspace for general-purpose document annotation, it is particularly well-suited for geo-annotation, in other words annotating documents with references to gazetteers, and supports the annotation of both texts and images (i.e., digitized maps). Already available for testing at http://recogito.pelagios.org, its formal release to the public occurred in December 2016.