The convent and castle complex are a historic and cultural monument and was listed as a UNESCO World Heritage site in 1983.

[1] Around 1190 it was encircled and resisted the armies of caliph Abu Yusuf al-Mansur who was successful in taking strongholds in the south.

[1] The castle became an integral part of the defence system created by the Templars to secure the border of the young Christian Kingdom against the Moors, which at the time occupied the area to approximately the Tagus River.

[1] As a result, at about the first half of the 15th century, work was completed to adapt the Templar oratory, introducing an open choir to the western niche, about half-way up the wall.

The Keep, a central tower of residential and defensive functions, was introduced in Portugal by the Templars, and the one in Tomar is one of the oldest in the country.

When the town was founded, most of its residents lived in dwellings located inside the protective outer walls of the castle.

The capitals of the columns are still Romanesque (end of the 12th century) and depict vegetal and animal motifs, as well as a Daniel in the Lions' Den scene.

The style of the capitals shows the influence of artists working on the Cathedral of Coimbra, which was being built at the same time as the round church.

The interior of the round church is magnificently decorated with late gothic/manueline sculpture and paintings, added during a renovation sponsored by King Manuel I starting in 1499.

A magnificent panel depicting the martyrdom of Saint Sebastian, by Portuguese painter Gregório Lopes, was painted for the Round Church and now hangs in the National Museum of Ancient Art in Lisbon.

From the outside, the rectangular nave is covered by abundant Manueline motifs, including gargoyles, gothic pinnacles, statues and "ropes" that remind the ones used in the ships during the Age of Discovery, as well as the Cross of the Order of Christ and the emblem of King Manuel I, the armillary sphere.

The so-called Window of the Chapter House (Janela do Capítulo), a huge window visible from the Saint Barbara Cloister in the Western façade of the nave, carries most of the typical Manueline motifs: the symbols of the Order of Christ and of Manuel I, and fantastic and unprecedented elaborations of ropes, corals and vegetal motifs.

The entrance of the church is done through a magnificent lateral portal, also decorated with abundant Manueline motifs and statues of the Virgin with the Child as well as the Prophets of the Old Testament.