- Short shorts
- Mini skirts
- Beach flip flops
- Crop tops, tank tops, tube tops, low-cut tops
In general, I'd recommend a few pairs of shoes for your trip to Spain:
- Sneakers
- Loafers or ballet flats
- Sandals (NOT beach flip flops)
T-shirts (no logos, please!), lightweight blouses, and even sleeveless tops are ok, but I'd avoid spaghetti straps or completely strapless shirts for tourism days unless you bring a wrap to cover that sleeveless top as needed.
Yes. It is almost certain that during your time exploring Spain this summer you will encounter at least one place, often churches and other affiliated religious sites, with a strict dress code.
A light cardigan should be sufficient unless you're planning a high-altitude trip. In big cities and beach towns, it'll be hot, hot, hot.
While it's ok to incorporate some aspects of your athleisure attire into your European tourism attire, you will look strange if you wear full yoga clothes while exploring Europe.