Originally a medieval castle called Kastello, it was destoyed in 1856 and resurrected in 1939. Now, it's the crown jewel of the Old Town. Inside, ancient mosaics bedeck the floors, and you'll find a unique collection of 16th and 17th-century Western furniture. On a hot day, the castle's massive walls provide a much-needed reprieve from the heat.

A tapering tower located south of New Delhi, Qutub Minar rises on a UNESCO World Heritage Site and one of the finest examples of the Afghan architecture that sprang up in the Islamic India from 1193. Thought to be a victory tower, it is said to be constructed to celebrate the beginning of the Muslim domination in India and, with the Qutub Complex, it is a show of that long gone majestic era.

More than just a bookstore, Livraria Lello is a historical and architectural masterpiece in downtown Porto. Opened in 1906, Livraria Lello & Irmão as it is also known combines elements of Neo-Gothic, Art Deco, and Art Nouveau styles that comprise intricate woodwork, a large stained glass window bearing the bookshop monogram with the motto "Decus in labore" (dignity at work, in Latin), and a remarkable red spiral staircase, which starts as one set of stairs and splits into two that join in a circular design. The latter is a huge attraction here since it resembles the Grand Staircase from the Harry Potter films, and considering J.K. Rowling was once a Porto resident, there is a high chance this place might have inspired her. Livraria Lello became so popular with tourists that in July 2015 the store started charging a 5 Euro entrance fee and queues can take over an hour. You can purchase tickets on their website.