The Church of Santa Eulàlia in Erill la Vall is one of the most refined Romanesque temples in the Boí Valley, part of the UNESCO World Heritage Site. Located in the centre of the town, the church fits naturally into the urban fabric and stands out for the elegance of its proportions and for one of the most slender and harmonious bell towers of the Pyrenean Romanesque. Built in the 11th–12th centuries, it has a basilical plan with three naves separated by columns and ending in semicircular apses. The construction is meticulous, with well-squared stone ashlars, and fully reflects the models of Lombard Romanesque. The six-storey bell tower rises with a very marked verticality, decorated with twin windows and friezes of arches that give it lightness and make it a dominant visual element of the town. Inside, the space is sober and balanced, designed for the liturgy and medieval community life. Although the original mural paintings are not preserved in situ, Santa Eulàlia is especially known for its relationship with the Descent from the Cross, an exceptional sculptural ensemble of Catalan Romanesque, now preserved in the National Art Museum of Catalonia. This fact reinforces the artistic value of the temple and helps to understand the cultural and religious importance that Erill la Vall had during the Middle Ages. The visit allows us to clearly understand the central role that these churches had within the community: spaces of worship, meeting and symbolic reference in a high mountain valley. Santa Eulàlia stands out for the harmony between architecture and environment, and is an essential stop to delve into the Romanesque of the Vall de Boí from a complete and contextualized perspective.