CLOSER (www.closer.ac.uk), funded by the ESRC and MRC, aims to maximise the use, value and impact of nine of the UK's longitudinal studies. A central component of CLOSER will be a metadata discovery platform that will enable the discovery of a range of data collection and variable metadata from each of the participating studies. The scale and detail of the metadata to be included will make it amongst the largest and most detailed of such repositories in the world. The discovery platform - nbsp;a customisation of the Colectica search portalnbsp; - will offer cutting-edge search technologies and innovative and user-friendly ways to discover, navigate and display the metadata. This presentation will describe how the metadata were created and harmonized, discuss how the search portal was built, and showcase the innovative search and discovery interfaces that are critical to allowing researchers to understand and leverage a massive data resource.