This was built in the 1720s in the reign of Ahmed III to defend the harbour, an Ottoman navy base against pirates and other foes. It's a rectangle of about 38 m x 76 m near the cliff edge, and once contained a mosque, baths and some two dozen houses. Water was piped in from 5 km away. It's said that convict labourers used in the construction were released upon completion and settled locally. The walls and watchtowers have been well restored. Enter via the east gate.
Ἀπόλλων Σμινθεύς
This is a Hellenistic temple from around 150 BC. It stood in the much older settlement of Hamaxitus, which means "wagon way" – a track led down to a harbour. The name of the temple is a puzzle: Smintheon is the deity beseeched at the opening of Iliad, something to do with mice or diseases that they spread. But the word isn't Greek, so it's unclear just where it got started between here and Cape Dezhnyov.