Karakoy stop, metro train. In the distance is the New Mosque, completed in 1663. Construction had begun in 1597 but suffered a serious setback as a fire and near complete structural collapse delayed completion. The metro crosses the Galata Bridge which was originally built by Justinian the Great in the 6th century.
Any visitor to Istanbul who has a day or two to burn should spend it riding these metro and tramvay lines. Get off on random spots that strike you as particularly beautiful or horrible. There are hidden treasure everywhere. Buy a refillable plastic metro card and go sip tea or raki in random alleyways. You will make interesting friends.