Chania old town is delightful. Its full of tiny back alleys with 4 and 500 year old buildings. The harbour and old town area will take you a couple of days just to figure out where everything is. Evening activities are centered at the Venetian harbour which is lined by tavernas and bars, Nothing rowdy though.
Chania is also a good base for day trips. The famous Samaria gorge hike is a favourite (for people who can hike downhill for 16 km) There is an excursion boat from Kissamos to Gramovossa island to visit a pirate fortress and also the Balos Lagoon beach. Ancient Aptera is a wonderful ancient site with over 5,000 years of history scattered on a mountain top.
You can easily do a day trip to Rethymnon to visit the Fortezza or take the bus south to the Lybian Sea to visit Elafonissi beach or a tiny village like Sougia for a day of beaching and a bit of hiking.
Depending on what interests you it would be possible to stay in Chania for a week to do some of the day trips.
Western Crete flickr.com/photos/…
Aptera images 38-62 Balos Gramovossa images 79-106
Chania flickr.com/photos/…
Theotokopoulou St area flickr.com/photos/…