 The temple is an octagonal domed building with a nod to the Pantheon , Rome , constructed in undecorated brick with a single east @-@ facing entrance . It was built in the Classical style popularised by the Italian architect Palladio with an Ionic portico , four columns wide by three deep , flanking the entrance . Several steps lead up to the portico . Inside , glazed arched windows reaching to the ground face the river . A deep curved recess in the west wall provides room for a statue . Outside , a lawn and garden provide views over the Thames to the south . 
