Complex sentence: Visitation of the dome is highly restricted, usually offered only to members of Congress and their select guests, and involves ascending a cramped elevator followed by a series of metal stairs between the inner and outer domes.
Split into simpler sentences: Visitation of the dome is highly restricted, usually offered only to members of Congress and their select guests. Visitors ascend in a cramped elevator followed by a series of metal stairs between the inner and outer domes.