identify this movie - Astronauts on a red planet with a pyramid/statue

I'm trying to find an old sci fi movie. All I remember is that a few astronauts have a station on this red planet (I think they have plants inside) and there's a big pyramid or some kind of statue on the planet. At the end of the movie they enter it and you don't know what happens next. I know for sure that it's not Total Recall or Stargate.