The persistent tension between low-redshift distance indicators and the Cosmic Microwave Background (CMB) radiation constitutes one of the key mysteries in present-day cosmology. While this discrepancy is often considered solely in terms of the Hubble constant, in this talk I examine the tension in a broader framework by including constraints from Baryon Acoustic Oscillations on the sound horizon, in addition to observations of gravitationally lensed quasars and the classical distance ladder. In order to reconcile the tension, several modifications of the standard LCDM model have been put forward. I talk about the current status of tensions between the CMB-based and local distance calibrations, as well as critically review the most popular extensions of LCDM proposed to reconcile these measurements.
