Westminster Cathedral
This is the main church of the Catholic Church in England and Wales. Construction began in 1895 and it opened in 1903. It has a neo-Byzantine style, with typical mosaics. It is still not finished yet, mainly due to lack of resources, and it continues to receive donations to complete it. The tower (87m), and the choir, are most striking. The choir singing in the cathedral is one of the most prestigious in the world, first for its acoustics and also for being the only cathedral that celebrates a sung Mass every day. Highly recommended.