The valley packs in more than a single base can cover. Manali, an hour and a half north, is the obvious onward stop and has plenty of its own POIs. Closer day trips from Kullu town include Bijli Mahadev temple on its ridge to the east, Naggar with its medieval castle and Roerich house, and the side valleys of Parvati (Manikaran, Kasol) and Tirthan for nature and quiet.
Bhuntar at the mouth of the Parvati is mainly an airport and bus junction, but the temples of Bajaura — including the Basheshwar Mahadev — are a worthwhile half-hour stop on the way south.