Jesus sees some fancy rich people making their tithes and a poor widow donating 2 cents. He says the widow is better than the proto-Romney because her contribution is an actual sacrifice.
Trying to change the subject, someone comments on the lavish riches that have been put into the temple. Jesus continues to be scornful, saying that it will all be gone sooner rather than later. Well, there is still a wall but alright.
Then he starts talking doomsday: famine, earthquakes, false Christs, persecution. But not to worry! They'll be fine. Pregnant or nursing women? Not so much.
Jesus promises to return on a cloud. The signs will be like spring, when the leaves start to bud on the trees. All this is supposed to happen within the Apostles' lifetimes, even though the Gospel of Luke is widely accepted as having been written between 75 and 100 AD, or at least 40 years after all this supposedly happened, when, first century sanitation and medical care being what it was, they would all have been dead already. Nonetheless! They should all prepare by being abstemious, lest this prophecy come to pass while they're in a drunken state of depression.
That night he goes up to sleep on the Mount of Olives and comes back down in the morning to pray some more.