Step through the impressive, pre-Justinianic marble portal (its huge blocks likely plundered from the nearby Temple of Artemis) to approach the basilica. In the 6th century AD, after earthquakes destroyed the modest church believed to mark the grave of St. John the Evangelist, Byzantine Emperor Justinian and his wife Theodora commanded that a grand marble basilica be erected over the site on Ayasuluk Hill, its eleven domes grand enough to rival the imperial pair's other legendary building project, Haghia Sophia. The basilica's barrel-vaulted roof collapsed after another long-ago earthquake, but the ruined church is still an incredibly evocative sight, with its labyrinth of halls and marble courtyards, and occasional mosaic fragments. It provides stunning views of Selçuk's castle, the Plain of Ephesus, the Isa Bey Mosque, and of towering Ayasuluk Castle (still closed after almost two decades of restoration work, but expected to reopen in 2014). Come by in the late afternoon when there are rarely crowds, pick up a brochure at the ticket office, and ramble around the site. Unscrupulous dealers in dubious "antiquities" cluster around the gates; they should be ignored.