Complex sentence: The Wall is 300 miles long (100 leagues) and over 700 feet high, it extends from the Frostfangs mountain range in the west to the Bay of Seals in the east.
Split into simpler sentences: The Wall is 300 miles long (100 leagues) and over 700 feet high. It extends from the Frostfangs mountain range in the west to the Bay of Seals in the east.