The 17th century St Paul's Cathedral on Ludgate Hill is one of the capital's most iconic buildings. Designed by the illustrious Sir Christopher Wren, St Paul's was the tallest building in London until as late as 1962. Use the touchscreen multimedia guides or take a guided tour to learn about the famous interior or, if you're feeling fit, climb up to the Whispering Gallery and try out the acoustics. From there you can carry on making your way up to the Golden Gallery atop the dome, where you'll be rewarded with breathtaking views of London. You can also descend into the crypt where you'll find memorials of important historical figures such as Admiral Lord Nelson.

Once the residence of Travancore royals, the roughly 200-year-old Puthe Maliga Palace (also known as the Kuthira Malika) has been converted into a fascinating museum containing historical artefacts pertaining to the Travancore dynasty. A guided tour of the palace is included in the ticket price; admission to palace grounds is free.

This beautiful example of Spanish colonial architecture contains a small museum dedicated to the Spanish Inquisition's brutal persecution of heretics once carried out in these very chambers. Visitors can still see some of the torture devices used to extract confessions of heresy and witchcraft, along with some of the questions used in "witch" interrogations, which are still displayed on the museum wall. Needless to say, no prisoner could hope to be acquitted of their purported crimes against the Catholic Church, and most met their tragic end at the very guillotine still on display in the courtyard.

Visible from almost everywhere in Cartagena, the Convent of Santa Cruz de la Popa all the way up the 150-metre hill known as Mount Popa. The hill got its name for resembling a poop deck of a ship. After four centuries of varied history, the convent itself is now open as a religious museum. From the top Mount Popa you’ll get the best panoramic views of Cartagena and its beaches. The fastest and least stressful way up the hill is with a taxi (be sure to haggle on the price). Important tip: if you take a taxi or a car service to this location, pay them a few pesos to wait for you to drive you back. The taxis on top are all already "reserved" and Uber drivers are not eager to drive all the way to the top to pick you up.