Pay a visit to the caves, a geomorphological monument to nature near Porec.  Signposted Pazin.  http://www.istra.com/baredine/nem

Visit the 3,000 year old town and its arena.  http://www.istra.com/pula/nem/

Whole day trip via the hydrofoil to the eternal city, world-renowned for its typical gondolas.  A sightseeing tour of the city takes approx 7 hours and includes St Mark’s Basilica and square and the Doge’s Palace.  The afternoon is spent wandering through the lively streets leading to the Rialto Bridge and the Grand Canal, on to the Bridge of Sighs in the tourist areas.  It is also possible to visit the glass factory of Murano..  There would also be an opportunity of taking a gondola or a motor boat through the canals.  Lunch is extra, but at a reasonable price.
Information from the Tourist Bureau.

Take a trip to the islands nearby.  There are daily ferries and car ferries.  One of the most beautiful in the world is Hvar.