The Gherkin is the popular nickname for the office block opened in 2004 at No.30 St Mary Axe. The road is named after the nearby Church of St Mary Axe (the 'axe' part referring to a relic kept in the church). The skin of the building is double-glazed and the space between the glazing is ventilated to help with temperature control and reducing energy use. The Gherkin is said to use only half the energy of similar sized office towers. Most of the panes of glass are completely flat - the only curved glass is the 'lens' at the very top. Each floor has been rotated 5 degrees relative to the floor below. The top of the tower has been kept as an open space to give an uninterrupted, all-round view.