The bent pyramid, considered to be the first 'real' piramid in Egypt. It is about 4600 years old. That is of course not really infinite but I remember how I was standing there in the desert trying to imagine how thousands of years ago people were building this structure because of their religion and the structure of their society. The religion doesn't really exist any more, that society is gone but this remnant has survived. And who knows how long it will stand here in the desert?