CartoSet is a new Open Source framework to develop great geospatial websites. Based on the experience by Vizzuality developing highly visual geospatial websites, like protectedplanet.net, CartoSet is a Ruby on Rails framework based on CartoDB. Despite the number of existing geoportal websites none of them allow the creation of highly customized interfaces. On the other hand libraries like geoRuby provide great foundation but still it takes too much time to develop nice websites. CartoSet is a FOSS framework in the middle, allowing great customization but providing an easy building block for agile developers.