The correct option is 1 and 3 only.
Explanation
The Sun Temple at Konark (13th Century AD) is the pinnacle of the Kalinga school of temple architecture (a sub-style of the Nagara order). It was commissioned by King Narasimhadeva I of the Eastern Ganga dynasty.
Statement 1 is Correct: The temple is located at Konark on the shores of the Bay of Bengal in Odisha. Historically, it was used as a navigational landmark by European sailors, who referred to it as the "Black Pagoda" due to its dark appearance, in contrast to the "White Pagoda" (Jagannath Temple) at Puri.
Statement 2 is Incorrect: The temple is architecturally designed in the form of a colossal chariot of the Sun God (Surya), drawn by seven horses. The base (plinth) is not plain; it is adorned with 24 intricately carved stone wheels (representing the hours of the day or the fortnights of the year). The walls are heavily embellished with sculptures of musicians, dancers, and erotic figures (Mithunas), making them far from plain.
Statement 3 is Correct: The main tower (Vimana) has collapsed, but the assembly hall (Jagamohana) remains. The temple features three subsidiary shrines with images of the Sun God positioned to catch the sun at dawn, noon, and sunset. The massive sculpture of Surya on the southern wall is carved out of green chlorite stone (often referred to as green stone) and depicts the sun in its mid-day phase.
Key Takeaway: The Konark Sun Temple is a Kalinga-style architectural marvel designed as a chariot with 24 carved wheels. It was built by Narasimhadeva I and is known as the Black Pagoda.