Water stays in vapor form, and is eventually broken into H 2 and O by UV photons. H 2 escapes, causing Venus to dry out. The surface of Venus has been mapped using imaging radar. These are not ancient highlands like the Moon. Also identified impact craters, volcanoes, and other geological features.
High temperatures makes the crustal rock soft.
Upwelling material from the mantle. Downwelling causing compression. Randomly scattered around the surface. Craters get filled in by volcanoes very quickly. This difference may be related to lack of water in Venus' crust, which makes it more pliable than the Earth's crust.