Tower of London

Many say the Tower of London -- which actually comprises 20 towers -- is a must-see. Although its exterior might be grim and even unimpressive, especially when compared to Buckingham Palace or other castles of the United Kingdom, inside you'll find the Tower is bustling with activity. You can view the famous Crown Jewels at the Jewel House, you can take a free guided tour led by the Beefeaters (Tower guards), you can climb the White Tower, and you can bid hello to the ravens that occupy Lanthorn Tower, among many other activities.

The majority of travelers say the Tower of London's high admission price is worth every pence. And recent visitors recommend attending the 10 p.m. Ceremony of the Keys for an ambient/creepy experience (imagine all those who were executed in this very place). Open daily, the Tower of London is located off the Tower Hill tube stop.

• See history come alive -- go to the Ceremony of the Keys at the Tower of London. This ceremony, the locking up of the Tower, has been performed every night at 10PM for 800 years. Tickets are free but MUST be prearranged." -- Wikitravel