The speaker declares that he has found the most beautiful scene on earth. You'd have to be someone with no spiritual sense, no taste for beauty, to pass over the Westminster Bridge that morning without stopping to marvel at the sights. London is wearing the morning's beauty like a fine shirt or cape. London, you're lookin' good.
The time is so early that all is quiet. The various landmarks visible from the bridge, including St. Paul's Cathedral and the Tower of London, stand before him in all their grandeur in the morning light. Fortunately, there happens to be no "London fog" to obscure the view.
The speaker compares the sunlight on the buildings to the light that shines on the countryside, and he seems surprised to feel more at peace in the bustling city than he has anywhere else. The River Thames moves slowly beneath him. In a burst of emotion, he pictures the city as blissfully asleep before another busy day.