Iglesia de San Diego, Byzantine church in San Diego, La Unión, Costa Rica.

The iglesia de San Diego is a church with Byzantine architectural style in San Diego, La Unión, featuring an open interior space without columns. At its center sits an octagonal baptismal pool surrounded by mosaics depicting the four evangelists.

Before 1990 the community was a filial of the Nuestra Señora del Pilar Parish in Tres Ríos. Father Heliodoro Granja founded a pastoral centre in San Diego, and on 13 November 1995 Father Walter Arce Ulate raised the church to parish status. On 9 June 2004 Bishop Hugo Barrantes Ureña approved the new temple project, and construction began on 1 August 2005 with 15 million colones.

The parish brings people together through different apostolic groups, including Neocatechumenal Communities and the Legion of Mary, which organize regular meetings for spiritual development. These groups shape daily community life and form the heart of local activities.

Access is straightforward since the building is located in San Diego with an open layout that is easy to navigate. Visitors should plan their timing around local services to experience the community worship and see how the space is used during gatherings.

The parish was raised to that status on 13 November 1995, the feast of its patron, under the priest Walter Arce Ulate. It brought together the communities of San Diego, Santiago del Monte, Calle Girales, Calle Mesén, Villas de Ayarco, Montufar and San Juan. The new temple project was approved on 9 June 2004 by Monsignor Hugo Barrantes Ureña, who set aside the first architect's plans.