London, United Kingdom 

 An architectural masterpiece of the 13th to 16th centuries, Westminster Abbey has become a treasure house of artifacts. This gothic abbey church in London is also the coronation church where some of the most significant people in Britain's history are buried or commemorated. 

 While a general visit to Westminster Abbey requires a ticket, you can enter for free to attend church services, disabled visitors and their caregiver receive free admission, and children under 5 are admitted free when accompanied by an adult.