Which are the 2 famous monuments of the medieval period?

The medieval age covers about one thousand years beginning around 500 CE. If you are talking about buildings which people made in that time, just look to the cathedrals of Europe. If you are talking about the Americas, then look to the Mayan cities of Tikal, Palenque, and Copan. There is also the Aztec city of Tenochtitlan and the Incan city of Machu Pichu. There was also Pataliputra, the capitol of the Chandragupta Empire of India. Unfortunately, it is in ruins under the modern city of Patna.