Answer:
The Astrolabe was invented so that Muslims could know
their location. This was important because when they pray, they
face Mecca. It could find the position of the Sun, Moon, and
stars from any position. Eventually, the Muslims were able to
find the approximate size of the Earth.
Algebra I believe one of the most fascinating achievements the Muslims made was the invention of Algebra. It all started with Muhammad al-Khwarizm. He wrote multiple books dealing with numbers and Indian mathematics. In one of his books, called al-jabr, he created a whole different style of math, Algebra.
Calligraphy was another achievement for the Muslims. They used calligraphy patterns to cover walls, floors, and ceilings. Another place they used calligraphy was in their beloved Qur'an. Calligraphy also was used as decoration on vases and swords due to their intricate patterns.
Hope this helps!
~PumpkinSpice1