The Tower of s. Sebastião, current Museum-Library counts of Castro Guimarães, dating from the early 20th century and was built on the initiative of the aristocrat Jorge O'Neil.
Remarkable work of romantic architecture, the Tower of s. Sebastião fascinates by mixing styles and by engaging a mysticism that makes you wonder stories of other times.
In 1910, the Palace was sold to the counts of Castro Guimarães, after carrying out some changes, began to inhabit him most of the year. The good taste of the couple reflected in the acquisition of works of art and furniture from various eras, as well as his interest in culture is felt in the purchase of two of the most significant elements of the acquis of the current Museum: a neo-Gothic organ built to order to the count and valuable Chronicle of Afonso Henriques, of Duarte Galvão.
The Earls enjoyed a short time of this magnificent palace. When he died in 1927, the Earl left, in her will, the House and property to the municipality of Cascais, for which it was constituted a House-Museum and public gardens. The Museum-Condes de Castro Guimarães Library was officially inaugurated on July 12, 1931, having been for many years the only one existing in the municipality of Cascais.
The educational service of the Condes de Castro Guimarães Museum has been in existence since 1964, when started the guided tours for school groups and the workshops of Visual Arts. This sector constitutes the main interlocutor between the Museum and the public.