Beneath this gate there is a remarkable tunnel called the Ponte Sodo, bored in the volcanic rock for the passage of the river.  It is not, however, visible from this point.  You require to descend the steep banks of the river to see it; and a very extraordinary excavation it is, two hundred and forty feet long, sixteen feet wide, and twenty feet high.  It was doubtless made to prevent the evil effects of winter floods by the inhabitants of Veii, who had considerable skill in such engineering works.  The river sometimes fills the tunnel to the very roof, leaving behind trunks and branches of trees firmly wedged in the clefts of the rock in the inside.  It was extremely interesting to stand on this spot and see before me this wonderful Etruscan work, and to lave my hands in the waters of the Formello, which, under the classical name of the Cremera, was prominently associated with early Roman history.  It would be difficult to find a lovelier dimple in the fair face of mother earth than the valley through which the Formello flows.  Precipitous cliffs rose from the bed of the river opposite to me, enriched with all the hues that volcanic rock assumes under the influences of the weather and the garniture of moss and lichen.  A perfect tangle of vegetation crowned their tops and fringed their sides; the dark unchanging verdure of the evergreen oak and ivy contrasting beautifully with the tender autumn-like tints in which the varied spring foliage of the brushwood appeared.  Bright flowers and gay blossoms grew in every crevice and nook.  The shallow river flowed at my feet through ruts of dark volcanic sand, and amid masses of rock fallen from the cliffs, and stones whose artificial appearance showed that they had formed part of the ramparts that once ran round the whole circuit of the heights.  The sunshine sparkled on the gray-green waters, and followed them in bright coruscations for a short distance into the mouth of the tunnel, the other end of which, diminished by the distance, opened into the daylight like the eye-piece of an inverted telescope.  I found in the bed of the river fragments of marble and porphyry, cut and polished, that had doubtless come from the pavement of some palace or temple, and attested the truth of the report that has come down to us, that the buildings of Veii were stately and magnificent.  To me there is something peculiarly impressive in the presence of a stream in a scene of vanished human greatness.  Its eternal sameness contrasts with the momentous changes that have taken place; its motion with the death around; its sunny sparkle with the gloom; while its murmur seems the very requiem of the past.  In this giant sepulchre, into which, like the Gulf of Curtius in the Forum, all the greatness of Etruscan and Roman Veii had gone down, the abundance of life was most remarkable.  The vegetation sprang up with a rank luxuriance unknown in northern latitudes; lizards darted through the long grass; one snake of considerable length and girth uncoiled itself before me and crawled leisurely away; and the air, as bright and warm as it is in July with us, was murmurous with the hum of insects that danced in the April sunshine.