An obelisk is a tall and tapering pillar-like monument with four sides, and has a shape that looks like a pyramid at the top. Originally, obelisks were monolithic, but over time, more and more obelisks came to be built of several stones. Some modern obelisks even have interior spaces. Let us take a look at 10 Amazing Obelisks in the World. World's 10 Most Amazing Obelisks.