If you're able, you should climb the 72 steps (very steep) to the top of the Lost World.
If you are coming in from another country, I have read that crossing the border into Guatemala can be very dangerous. It is best to fly in to Flores, or go as part of a tour.
I suggest you go with a guide who can not only narrate the history of the the ruins, but fill you in on the wonders of the surrounding jungle as well.
Wear good walking shoes and be prepared to climb and balance. To see all that Tikal has to offer, you will need to be a bit adventurous!
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