It is standard for apartments to be leashold rather than freehold. This is because where your apartment is part of a larger building, it is not possible to own the freehold - the common areas such as hallways, stairwells, etc, as well as the external fabric of the building have to be held in common by the apartment owners. I'm not entirely sure, but I presume the freehold of the site would be owned by the managment company, of which all apartment owners are members.
100 years would be unusually short for the lease - in my admittedly narrow experience, 999 years would be typical. Maybe someone with legal experience could comment. Anyway, after 999 years, the OP and his heirs will be long past caring what happens!