HELP! Where to stay in Europe for three weeks?

I am doing a trip where I will be shadowing doctors for THREE weeks somewhere in Europe. I have a bunch of options to choose from and can't decide for the life of me. Here are some of the things im looking for/like. Any recommendations or suggestions would be so helpful. I am treating this a "graduation trip" as someone who is a complete newbie for traveling.

- Im a 21 year old college student that will be traveling with a small group of random people around my age.

- Not a huge crowd/party guy but still want a place with decent night life.

- Not really a tight budget.

- I will be in hospitals for 4-5 hours for four days a week. Any experiences with the hospitals of these places? Are any of them really nice or any I should avoid?

- Love good scenery/nature

Here are the options the program gives:

Padua, Italy

Arezzo, Italy

Mestre, Italy

Coimbra, Portugal

Agios Nikolaos, Crete

Split, Croatia

Any advice would be amazing! Thank you!

Author: Bauxes_