The winding stretch of the Danube River from Budapest, Hungary to Regensburg, Germany is a cruising classic. Lined with Baroque architecture, towering castles, and quaint towns threaded with cobble stone streets, the river is a gateway to a handful of bucket-list sites. And with excursions often covered in the cruise price, you don't have to plan — or even think about — most of your sightseeing.

If you're not joining a guided tour, however, or just want to spend some time wandering on your own, you don't have to spend a lot to see a lot. Here are some of our favorite places to spend free time on a Danube river cruise — all of which were uncovered when we recently cruised on the Gate 1 Monarch Empress.

Passau, Germany

Go Gaga at the Glasmuseum

Central Europe was once one of the prime glassmaking regions of the world. In this sprawling museum set into a restored historic building, you'll see the results of centuries of industry. There are entire sections strikingly organized by a single era, type of object, or by color. You can spend hours here studying Art Nouveau vases, etched crystal punch bowls, or jade glass candlesticks. Don't feel pressured to see the entire museum — with 30,000 objects in the collection, it's unlikely you'll get to everything.

Price: Admission is 7 euros (about US$9) for adults and 5 (US$7) for kids.

See What You Can Hear in the Cathedral

St. Stephen's Cathedral has a riotous baroque interior and is home to the largest cathedral organ in the world (it has more than 17,000 pipes). Try to catch an organ concert while you're in town for the day. They're typically held weekdays and Saturdays at noon from May to October.

Price: The church is free to enter when there isn't a concert; organ concert tickets typically cost 4.50 euros (US$6).

Regensburg, Germany

Stop for a Drink — or Four

Regensburg is the final stop on many Danube itineraries. When you're not wandering amidst the town's pretty Medieval buildings, stop into the Rengensburger Weissbrauhaus for German beers and Bavarian food. Sample all of the brewery's offerings with small tastings of single beers, or order a flight of four.

Price: Pay about 5 euros (about US$7) for a four-beer tasting flight or about 1.10 euros for a sample size of each beer.

Cezky Krumlov, Czech Republic

Explore Modern Art in Antiquated Surroundings

To reach this Czech town, you'll likely need to pay extra for an excursion that includes the hour-long bus transfer. Once you're there, though, the thrills are plenty — and cheap. When you're through snapping photos of the town's turreted towers, picturesque bridges, and painted stucco, stop for a look at some of its more modern history. Early expressionist painter Egon Schiele lived in Cezky Krumlov and is honored with a museum here. It houses exhibitions by Schiele as well as other modern artists and seems almost out of place among the town's old-fashioned architecture. If you're not up for this kind of art — Schiele led a troubled life and some of his work is controversial — skip the museum and head next door. The eponymous cafe feels like a perfectly rumpled, atmospheric spot where artists can crash with a book, a sketch pad, and a cup of coffee. Grab one of the overstuffed chairs and order the apple strudel, which is made fresh each day.

Price: Museum entry costs 9 euros (about US$11); coffee and strudel at the cafe will set you back about 6 (US$7).

Bratislava, Slovakia

Get Coffee With the Cool Kids

As Bratislava continues to shake off decades of isolation and poverty under communism, you'll see growth — and its young, energetic populace — everywhere. Our favorite spot in town, Urban House, is a bastion of this new guard. It's a design-conscious coffee shop, bar, restaurant, and performance space. We went for the bakery treats and coffees — the tumeric latte was a favorite — but the menu includes everything from pulled pork sandwiches to avocado toast.

Price: The fancy coffees will cost you about 4 euros (US$5), while snacks, appetizers, and tea come in around 4-9 euros each (US$5-$11).

See What's Buzzing

Founded by a family of beekeepers who've been running similar businesses for generations, Caramel Shop stocks beeswax candles, honey, mead, and all kinds of bee-related products.

Price: You'll find plenty here to take home for 5-10 euros (US$6-$12).

Vienna, Austria

Get Bookish

Austria's stately capital is crammed with awe-inspiring architecture. The city's famous Scheonbrunn Palace is a must-visit for its glittering interiors, but you'll likely have some additional time while you're in port to see a second site. For a quick, affordable, and uncrowded outing, head to the Austrian National Library and its magnificent State Hall. (There's no need to buy a combination ticket to view other parts of the complex unless a specific exhibit catches your eye.) With books stacked to the 60-foot domed ceiling, a visit here is like stepping into a fairy tale.

Prices: Tickets cost 8 euros (about US$10), with discounts for kids and seniors.

Linz, Austria

Go Mod at the Museum

Many river cruisers simply use their stop in the town of Linz to transfer elsewhere for the day — mainly, to the beautiful Czech town of Cezky Krumlov (mentioned above). If you're skipping this excursion and just want a relaxing day in port, or if you have some time after you return from your day of touring, there are more than a few worthwhile sites here within easy walking distance of your ship. You can't miss the Lentos Kuntsmusem, especially in the evening. This modern glass block situated directly on the river is lit with a shifting palate of colored lights. Take a walk over (and under!) the structure to get a closer look, or step inside to wander around its bookshop without paying a cent. For a deeper dive, an entry ticket gets you access to the museum's formidable permanent collection — think Andy Warhol and Gustav Klimt — plus any temporary exhibitions.

Price: Admission costs 8 euros (US$10) for adults, with discounts for kids and seniors.

Kick Back on the Grass

Step off your ship, and you'll likely be standing in it, or at least near Donau Park. Linz's serene riverside park is a perfect place to stretch your legs, take a short walk, and get a glimpse of daily life in town. Locals meet up, walk their dogs, jog, and enjoy the views here. Join them for an an hour of respite before you head back onto your ship for dinner.

Price: Free