Complex sentence: There are currently 12 structures in the city over 150ft, the majority of these were built in the 1960's and 1970's, since its completion in 1854 the 308ft tall Church of St. Walburge has remained the tallest building in Preston.
Split into simpler sentences: There are currently 12 structures in the city over 150 ft; the majority of these were built in the 1960s and 1970s. Since its completion in 1854 the 308 ft tall Church of St. Walburge has remained the tallest building in Preston.