Simplify the following text for a Grade 3 native English-speaking person.
Original: SÃ # o TomÃ is centred on a sixteenth century cathedral . Another early building is Fort SÃ # o SebastiÃ # o , built in 1575 and now the SÃ # o TomÃ National Museum .
Simplified: SÃ # o TomÃ is important as a port .