@wtruckyboy
You're right that it's quite hard to find a totally free activity! But I think low-cost gives us a bit of leeway. :-)
As we're in Bulgaria, I think many paid activities are quite accessible.
I'm in Plovdiv, but I'm sure most Bulgarian cities will have similar options.
There are several nice malls here, Mall Plovdiv is my nearest. I can do a walk down there, and have a stroll around in air-conditioned comfort on a 35 degree day. A coffee is a couple of leva.
Opera in the Amphitheatre starts at 10 euros, as I mentioned. But cinema and museum entries are usually less. There are several cinemas and a number of museums and galleries here. Just visiting the Amphi during the day is a few leva.
The Plovdiv Old Town is a great location, with lots of cobbled streets and old Bulgarian houses. This is a free walk, of course.
Plovdiv also has Kapana, a bohemian cafe/bar area in the style of Brighton's Lanes which is nice to stroll around, especially in the evenings when the lights are up. A few leva for a beer / water / tea / coffee even in this trendy zone.
Plovdiv has multiple Roman/Greek ancient ruins which have been preserved and opened to the public. Most, including the hippodrome in the centre, are free. Any attached museums are very inexpensive to enter. Ditto the Amphi, the jewel in the crown.
Plovdiv has generous green areas, all of which are free to enter. There is the central park with Singing Fountains, also lovely at night. Nice pedestrian-only paths to the top of its famous hills. The regatta lake has a walking/cycling path. The Maritsa River has riverside trails.
It's not just the big city that can keep us occupied. Our village house is in the Balkan Mountains between Shipka and Kazanlak. This has turned out to be a super area. (And I think there are lots of attractions in many other regions.)
- mountain trails for walking and cycling starting in my village, and several others
- this area is known as the Valley of the Roses, the centre of rose oil production in Bulgaria. There is a big annual festival and multiple rose-related museums/attractions.
- this area is also known as the Valley of the Thracian Kings due to the ancient city and burial mounds of the Thracian civilization in this region. Multiple tombs to visit (including the biggest one in Kazanlak) all with very inexpensive admission (a few leva).
- The Central Balkan National Park is very large, and very beautiful, and only a few km away. This has hardcore multi-day hikes, and gentle family excursions on various eco-trails. There is a gondola at Sopot (next to Karlovo) to get you quickly to the top (to walk, bike, or enjoy the view).
- Shipka church and Shipka memorial.
- Koprinka reservoir for fishing and boating.
- Neighbouring Pavel Banya spa town.
- Monastery at Maglizh.
- Buzludzha Monument is well worth a visit, and this also has a national park area including the Shipka Monument and the forest between the two.
In general, Bulgaria has loads of very nice churches and monasteries. Admission is usually very minimal, and is often left up to you how many leva you want to put in the box or pay for the candle.
Plenty of seaside at the Black Sea coast. Who doesn't like a day at the beach?