Este não é um monumento, mas sim a máscara de Ra.
Na verdade, foi na introdução para todas as primeiras cinco temporadas, com a intenção de ser uma ligação visual com o filme, onde Ra tem uma máscara similar.
Quando se mudou para o Sci-Fi, uma nova introdução foi feita, incluindo temporadas antecipadas. Esta postagem do Reddit explica por que algumas temporadas mantiveram a abertura original:
The first five seasons, with Showtime, all used the Ra's mask intro when they originally aired. When SciFi picked up the series for season 6, they created a new intro, and also went back and made a new intro for the older seasons, the action-packed intro we all know and love.
However, since they changed from 16mm to 32mm film from the season 3 finale onwards, it created a weird situation where the new intro, meant for use in syndication, wasn't compatible with the DVD mastering process for some reason. So the DVDs (at least the first editions, not sure about the later ones) start off with the action-packed intro, then switch to the Ra's mask intro abruptly from the season 3 finale until the end of season 5.
Hope that helps. It's a source of some confusion, since some episodes might have a different intro depending on whether you saw them in syndication, or DVD/original airing.