Read this piece of letter and open the brackets (...)

Source: theculturetrip.com

Dear Mom,
I am in Semarang now. I pass through this amazing building. 
The building (1. be-establish) in the Dutch colonization era. It (2. can-see) from the architecture. I heard a sad history of it at glance, but I think the historical buildings (3. should-not-neglect) no matter how it was built and who built it. I think this building potential (4. can-explore) much better. Tomorrow I'll visit the building, let's see!

The most suitable phrase for point 4 is ...