The Temple of Kukulcan at Chichen Itza...

Famously known as El Castillo (the castle)this is the Temple of Kukulcan at Chichen Itza. Note the rope in the picture descending from the top of the pyramid. This is to aid visitors in their climb to the top and back but, still, it is not uncommon to see people panic half way up owing to the 45 degree angle and narrowness of the stairs (coupled, of course, with the great height). There are guides available at the site to help one back down though usually people manage to do so by themselves with or without the help of the rope.