Two churches in Meteora. Monastery of Great Meteoron has no online ticket listed; Meteora has 165 tickets and tours to book. The table and the two notes below put them side by side; the full pages have what to see, the ticket and the timing for each.
The Great Meteoron is the largest and oldest of the six monasteries still inhabited at Meteora in central Greece, perched on the highest of the rock pillars above the town of Kalambaka. Entry is ticketed, cheaply, and paid at the gate. The main practical points are that each monastery closes on a different day of the week, and the Great Meteoron is normally closed on Tuesdays, and that the monasteries close in the early or mid afternoon, so a tour that starts late may miss the interiors.
Meteora is not one ticket but six. Each working monastery on the rock pillars charges its own small entrance fee at the gate, payable in cash, and each keeps its own closing day, so the practical question is how you get between them rather than what you buy. Driving yourself is cheapest and most flexible, since the road loops past every monastery with parking at each. Tours from the villages below, Kalabaka and Kastraki, run half-day and full-day versions that usually include three or four monasteries plus the transport, with the entrance fees often left for you to pay.