A little off the tourist circuit, London's Kew Gardens are a UNESCO World Heritage Site.

Big Ben and the House of Parliament.

Central London has so much to offer, most travelers never make it beyond the innermost neighborhoods.

Seeing the main sights – like Big Ben, Buckingham Palace and the Tower of London – can easily fill a whole vacation. But for those willing to devote the time, some of London’s best sights are just outside the city limits.

Greenwich

The most-visited and easiest to see of these attractions is England’s maritime center, Greenwich. Greenwich long served as London's port and Royal Navy base. Since much of the power of the British Empire was naval-based, Greenwich became a major scientific center promoting the once-state-of-the-art technology that enabled UK primacy on the seas.

To see a prime example of this naval application of science, head up the hill from the Greenwich town center to the Royal Observatory (left).

It was here that a concerted scientific effort to determine longitude resulted in two complimentary methods (one time-based and one based on astral observation) being discovered. As a result, this location on the earth’s surface, known as the prime meridian, became the reference standard for both longitude and time worldwide.

While in Greenwich, make sure to visit the National Maritime Museum to see firsthand the Empire’s seafaring history. After visiting the museum, architecture buffs will want to see the former Royal Navy College (now the University of Greenwich).

You can reach Greenwich easily by taking the Docklands Railway (DLR) from the Canary Wharf tube station.

Windsor Castle

Windsor Castle has been the official residence of the English monarchy since the time of Henry I in the 12th century. It is also the largest inhabited castle in the world.

When visiting, be sure not to miss the Royal Apartments to view what everyday life as a royal is like. Another highlight is St. George’s Chapel, where you can get an inside view into the prestigious Knights of the Garter.

You can get to central Windsor from either Paddington or Waterloo train stations in London. It’s a short walk on well-marked streets to get to the castle from the train station.

Kew Gardens

One of the most overlooked sights in London are the wonderful Kew Gardens. Although missed by many international tourists, UNESCO has recognized these extensive gardens as a World Heritage Site for their impressive collection of fauna from throughout the world. Be sure not to miss the treetop walk for a hike on an elevated walkway at treetop height. On cold days, warm up in the iconic Palm House (top).

The Kew Gardens can be accessed via the last stop on the Richmond branch of the District Tube line. (Note that you’ll need a zone 3 ticket for the journey.) From the Kew station, the gardens are a 400-meter walk.