21. The Outlook Tower, Edinburgh

Source: https://c1.staticflickr.com/9/8074/8282880597_9ec26cdb2f_h.jpg
Topped by a camera obscura, this Gothic house dating back to 1776 was built to house scientific equipment maker Thomas Shorts' collection of instruments and telescopes.

22. Pierhead Building, Cardiff Bay

Source: http://en.wikipedia.org/wiki/Listed_buildings_in_Cardiff#mediaviewer/File:Adeilad_y_Pierhead,_Caerdydd.jpg

This French-Gothic Renaissance style building was constructed in 1897 to replace the headquarters of the historically significant Bute Dock Company which burnt down in 1892.