The trip to Semarang seems incomplete if you have not visited Sam Poo Kong Temple, the ancient chinese architecture building was made to commemorate the Admiral Ceng-Ho (Zheng-He). I traveled to this temple about a few years ago, it was a long time ago.
This red building witnessed the arrival of Laksama Chen Ho from China. In the pagoda that used to be a mosque, you can meet with the admiral and his legendary story.