Final answer:
The 'blue wall thing' is the Blue Mosque in Istanbul, known for its harmonious design including domes and minarets, and distinctive use of blue in its decorations.
Step-by-step explanation:
The structure referred to as the "blue wall thing" is c) The Blue Mosque in Istanbul. This iconic religious building is a prime example of Ottoman architecture, celebrated for its harmonious design that includes multiple domes, soaring slender minarets, and a balanced aesthetic that is both technically impressive and transcendently beautiful.
Ottoman mosques, such as the Blue Mosque, typically feature vaults, domes, square dome plans, slender corner minarets, and columns. These elements converge to create spaces that are not just places of worship but also sanctuaries of astonishing aesthetic and technical balance. The Blue Mosque's use of color, particularly blue, lends to its distinctive appearance and nickname.