What are the best day trips from Dubrovnik?

Lokrum Island is the lowest-commitment day trip from Dubrovnik. The ferry leaves from the Old Port every half hour in summer, takes 15 minutes, and costs about €15 return including the nature reserve entry. One of you can swim at the rocky cove on the island's south side, where the Adriatic tends to hover around 22°C in June, while the other explores the 11th-century Benedictine monastery ruins. The botanical garden smells like rosemary and wild sage in the afternoon heat. You'll hear Lokrum's peacocks before you see them. Mind you, the island closes at sunset with no overnight stays permitted, so plan to catch a return ferry by 7pm. Bring water from the Old Port, because the single café near the monastery charges €5 for a small bottle.

Ston, 55 km northwest on the Pelješac peninsula, is the best single-day trip for a couple where one wants to eat and the other wants to climb something. The bus from Dubrovnik's main station takes about 1 hour and costs around €8. Mali Ston, the smaller settlement 1 km north, has been farming oysters in the same channel since the 14th century. Bota Šare serves a dozen for around €12 to €15, still cold and briny from the morning pull. While the foodie lingers over a second glass of Pošip from the Pelješac vineyards, the history person can walk the 5.5 km of defensive walls that connect Ston to Mali Ston. They were built in 1333 to protect the Republic of Ragusa's salt pans, and the climb takes about 90 minutes with a few steep sections that get hot by noon. Meet back in Mali Ston for a late lunch.

Mostar over Kotor for a full day, if you're choosing one. Mostar is 130 km northeast in Bosnia and Herzegovina, about 3 hours by FlixBus from Dubrovnik for roughly €16 each way. The rebuilt Stari Most bridge (the original dates to 1566, destroyed in 1993, reconstructed in 2004) anchors a compact old town you can cover in 4 to 5 hours. The Kujundžiluk bazaar runs downhill to the Neretva River, and the copper workshops still operate at street level. You can hear the hammering from Stari Most. The bridge's limestone gets slippery when wet, so wear proper shoes. Kotor, 95 km south in Montenegro, takes about 2 hours by bus, but the border crossing can add 30 to 60 minutes in summer. The Bay of Kotor is worth seeing, and the 1,350-step climb to San Giovanni fortress gives a proper workout. The old town itself is smaller than Mostar's, though, and tends to fill with cruise passengers by 10am. If you do Kotor, take the earliest bus (usually around 6:30am from Dubrovnik's main station) and reach the fortress stairs before the 10am cruise crowds.

Cavtat and Trsteno Arboretum work as a combined day, and they're the right call when one partner is tired of long bus rides. Cavtat is 20 km south on bus 10, which runs every 30 minutes for about €2. The harbor promenade curves past the Vlaho Bukovac Gallery. Bukovac, Croatia's most noted Impressionist, was born in Cavtat in 1855. There's decent swimming off the rocks near the Franciscan monastery. Trsteno Arboretum sits 20 km north of Dubrovnik by local bus. The gardens date to the late 15th century, planted by the Gučetić-Gozze family and formally designated as a public arboretum in 1948. The two Oriental plane trees at the entrance are over 500 years old, with trunks you'd need 4 people to wrap your arms around. The 16th-century aqueduct fountain still runs. Entry is around €6. Worth noting, Trsteno doubled as King's Landing's gardens in Game of Thrones, which might matter to one of you more than the other. Do Trsteno in the morning and Cavtat in the afternoon, and you're back in Dubrovnik by 7pm for dinner.