One of my favourite places in Cambridge is, of course, Kings College. If you live within 12 miles from it you can get a pass for £10 that allows you to get in as many times as you would like in a three year period. You can apply for this card here.
Kings College's foundation began under Henry VI and took 70 years to complete. The chapel was started in 1512 and took until 1536 to finish. The stained glass windows were installed under Henry VIII. They were removed during the Second World War to prevent damage.
One of my most favourite things about Kings is that you can still see King Henry VIII and Anne Boleyn's (his second of six wives) initials still carved in the oak screen that he donated to the chapel. They were only married 3 years until he had her beheaded. If you have seen/read The Other Boleyn Girl by Phillipa Gregory, you should know some of the story. She is significant because their union began the divide between England and the Catholic Church. He wanted a divorce from his first wife, Catherine, who was previously married to his brother but he died shortly after.
The second thing I really like is the fan-vaulted ceiling. This is quite impressive and the one seen in this Gothic church is one of the biggest in the world. There are small keystones that are placed between them which is keeping the structure up. Thinking about how they built this place without the technology that we have today, it is mind boggling.
When you walk into Kings, it is quite serene and the ambiance is amazing. You can attend evensongs which I am told is just as good as the Carol Service performed on Christmas Eve.
If school is not in session, you will be able to walk around the rest of the grounds. You can take in how big this building is. There is a law that nothing is allowed to be built taller than Kings College unless they pay a huge fee to Cambridge University.
If you have time, two different views of Kings that are great are from The Backs (the other side of the river) and Great St Mary's Church which is right across the street from Kings.
If you have only time to see one thing in Cambridge, I think this is the thing you should see.
All the Best!
American to Britain