need to think of words which best fits in each gap

Task : You need to think of words which best fits in each gap My text:
 Yet the elegance of the building hides a multitude of personal and technical problems  (1)____________ occurred during its creation.
For over a century after work began inn 1296, the proposed dome was regarded as all (2)____________ impossible to build due to its enormous size. To this day, it remains the highest and widest masonry dome ever built. The dome´s architect was a man (3)____________ Filippo Brunelleschi. One of the most obvious problems he had was how to transport heavy building materials such as sandstone and slabs of marble a hundert metres (4)________ the ground and place them in position with the accurancy demanded by his design. The hoist that he created to overcome (5)_________ problem became one of the (6)______ celebrated machines of the Renaissance. Today, as then, there are 463 steps (7)____________ and summit.  (8)__________ other place offers such a panoramic view of the city. Thank´s in advance