In downtown Saint Paul, nearly hidden among the high-rise buildings, you can spot what’s believed to be the world’s first modern skyway. The small green structure is also the highest skyway in the Twin Cities.

The wee green-hued skyway was built in 1931, when the Merchants Bank merged with the adjacent First National Bank. After the merger, the passage was built to connect the higher levels of the two buildings.

Due to differences in floor heights, the skyway connects the 17th floor of the First National Bank building with the 16th floor of the Merchants Bank Building. The skyway is only available to tenants who work in the building, but you can view it from the street. From a distance, it looks like a green block strangely wedged between two classic figures of the Saint Paul skyline.