Complex sentence: The Museum also houses the stainless steel time capsule designed after a competition won by Santiago Calatrava, which was sealed at the beginning of 2000 to mark the 3rd millennium.
Split into simpler sentences: The Museum also hosts a stainless steel time capsule which was designed after a competition that was won by Santiago Calatrava. The capsule was sealed at the beginning of 2000 to mark the 3rd millennium.