Complex sentence: Being an important junction point in Russia between several riverways and railways, the city grew rapidly during the 20th century as well as being an important industrial town the first designs for a rapid-transit system were formed in the 1970s and construction began in 1980.
Split into simpler sentences: Being an important junction of several waterways and railways, the city grew rapidly during the 20th century and became an important industrial center. The first designs for a rapid-transit system were drawn in the 1970s and construction began in 1980.