Everyone wants to see the Pyramids at Giza in Egypt someday, but not many people realize that you can actually go inside of them. Gaining entrance to the Pyramids themselves is as easy as showing up between 8 am and 4 pm and buying a ticket, but getting inside the Pyramids requires a bit more work. Their interiors consist of narrow shafts leading to long-since ransacked tombs in the center of the building. If you get claustrophobic you might want to just appreciate them from outside.
Go with a tour group from a reputable hotel or travel agency, or if you go by yourself, get to the Pyramids as early as possible, at least an hour before doors open at 8 am. Only 150 tickets are sold in the morning for entry into the Great Pyramid and tour guides get most of these. The number is limited in order to preserve the interior from damage caused by water vapor in visitors' breath.
Visit the Pyramids from the outside even if you miss the first batch of tickets for the Great Pyramid, and a second batch of 150 tickets for the Great Pyramids goes on sale at 1 pm. For all tickets at the Pyramids, both general admission and tickets to go inside, make sure that you buy the tickets from the clearly marked Ministry of Tourism building located across from Mena House. A lot of conmen will approach you claiming to work for the government, wanting to sell you tickets or take you on tours. Ignore them and threaten to call the police if they become aggressive.
Visit the Second Pyramid (the Pyramid of Chephren) in the meantime. You can go inside for much less than the tickets to go in the Great Pyramid, and there is no limit to the number of tourists allowed to enter during the day. Keep in mind that if you are visiting during the summer it may be prohibitively hot to enter any of the pyramids except in the morning when the weather is relatively cool.
Don't ignore the smallest pyramid, the Pyramid of Mycerinus! It isn't always open to the public, and it is a short walk away from the other two pyramids, but this just means you are likely to have it all to yourself if it is open. With any luck, after visiting the other two pyramids, if you missed the first batch of tickets for the Great Pyramid, now will be a good time to go get one from the second batch. Or maybe you'll have worn yourself out from the smaller two and be ready to call it a day.