What features are used in the classic egyptian pyramid

They served as a pharaoh’s tomb.

Smooth white limestone once covered the hollow interior.

They have triangular sides.

for many centuries, the catholic church has been a patron of the arts. the church has used various scientific methods to maintain its power.

not 100% sure though!

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.