Hello! It sounds like you're planning a fantastic trip to some of Greece's beautiful locations — Sparta, Monemvasía, and Hydra!

Best Time to Visit:
Generally, spring (April to mid-June) and fall (September and October) are the best times to visit these places in Greece as the weather is pleasant, and the crowds are fewer than in peak summer.

Route and Accessibility:
You can start your journey in Athens, flying in from any major city. From Athens, Sparta is approximately three hours away by road. Monemvasia, on the east coast, is a 5-hour drive from Sparta. From Monemvasia, you can return to Athens, a 4-hour drive, and catch a ferry to Hydra, which usually takes around 2 hours.

Accommodation and Booking:
These locations offer a range of accommodations. It's best to book in advance, especially during high season. You might want to explore charming guesthouses in Sparta, unique hotels within Monemvasía's medieval fortress, or boutique lodges in Hydra.

Clothing and Essentials:
Given the Mediterranean climate, opt for light clothing for summer months. During spring and autumn, layers are beneficial. Don't forget a good pair of walking shoes, sunblock, a hat, and a swimsuit for the beautiful beaches.

Health and Safety:
Greece is generally a safe country to travel. Still, always have travel insurance, stay hydrated, avoid excessive sun exposure, and always keep emergency contact numbers at hand.

Local Etiquette and Respect:
The Greeks are hospitable and appreciate it when travelers attempt to speak a few words of Greek. Remember to respect religious sites, dress modestly where required, and respect local customs.